By the time Jesse Easterling stumbled into the Mount Everest emergency clinic, he was nearly incoherent. It was a chilly afternoon at Base Camp, May 17, 2009—two days before the beginning of summit season, when a clear weather window would send hundreds of climbers scurrying up the south side of the peak. Easterling, a stocky 27-year-old insurance salesman from Seattle, entered the clinic—a simple tent staffed by two doctors—wearing a T-shirt and talking gibberish.

“What’s your name?” asked Dr. Torrey Goodman, 53, an altitude specialist from Hawaii in her first season working on the mountain. Easterling mumbled something. She asked again. “What’s your name?” More gibberish; he couldn’t stop fidgeting.

Goodman and the other doctor in the tent, Eric Johnson, a former president of the Wilderness Medical Society, were alarmed by Easterling’s appearance. His arms were covered by a rash. Johnson would later testify in Boise, Idaho, that Easterling had a “buffalo hump,” referring to an abnormal fat deposit on his neck. The doctors spent 30 minutes trying to get basic information out of him, but he couldn’t focus. “Why am I so bloated?” he kept asking. “Why am I so fat?”

“He was completely confused ... almost manic,” Johnson recalled in a deposition.

Finally, Easterling conveyed that he was an Everest rookie climbing with Asian Trekking, a Kathmandu-based outfitter known for cheap rates—a full expedition runs about $40,000, or $30,000 less than what top guiding outfits charge. Easterling had just completed his last rotation on the mountain, to acclimatize before his summit bid, making it as far as Camp III, at 23,500 feet. He mumbled something about taking a medication, then stopping.

The doctors immediately sent a Sherpa to Easterling’s tent to collect any drugs he could find. When the Sherpa returned, the doctors gasped: he was carrying a tray full of dexamethasone, also known as dex, a controversial anti-inflammatory steroid. Prescribed to treat everything from tumors to asthma, dex has become popular among mountaineers in recent years because it can mitigate some of the effects of altitude sickness and high-altitude cerebral edema (HACE), like brain swelling, and because, when taken prophylactically, it can help climbers ascend quickly. Used to excess, it can also have dangerous side effects. On the tray sat 30 unopened vials of dex—more than Goodman stocked to serve every climber on Everest for an entire season. The Sherpa also handed Goodman a bottle of pills. At one point it had contained 90 doses of dexamethasone. Now it contained four.

“When did you start taking these?” Goodman asked.

“In Lukla,” said Easterling, referring to the tiny Nepalese village that is the launching point for most Everest trips and where he’d arrived nearly a month earlier. Goodman and Johnson were horrified—four weeks on dex followed by a cold-turkey stoppage is enough to shut down someone’s adrenal system. No experienced mountaineer would self-medicate for such an extended period prior to a summit bid.

Easterling would later testify that his physician back in Seattle, Keith Tang, a native of Cambodia who studied medicine in the Cayman Islands, had prescribed a thrice-daily dosage, similar to what Johnson would give an end-stage brain-tumor patient. When Easterling had gotten spooked by his appearance and stopped taking the steroid four days before stumbling into Everest ER, he’d sent his body into adrenal crisis and triggered a psychotic breakdown. “Instantly, we knew that Jesse was in a life-and-death fight,” Johnson says.

They called for a helicopter and put Easterling back on the drug at a lower dose to stabilize his adrenal system. Due to bad weather, it took two days to evacuate him. He returned to the Everest ER tent nearly a dozen times in that span, a neurological train wreck. “I’m too scared to be alone,” he’d say, shaking. “I can’t sleep. What happened to me?”

On May 19, Easterling was evacuated to Kathmandu. Before the helicopter took off, Johnson and Goodman each gave him the same instructions—something they’ve never said to another patient in their combined 50 years of experience. They told Easterling to find a good lawyer and sue his doctor.

That night, Easterling vomited half a cup of blood. He spent 12 days in a Kathmandu hospital, mostly in the intensive-care unit. He wailed in pain from severe gastrointestinal bleeding. The U.S. consulate in Kathmandu emailed Easterling’s mother, saying he was in critical condition. Eventually, he received a blood transfusion, stabilized, and flew home. Now, looking back, he says, “I got lucky.”

In the four years since Easterling’s meltdown, his story has gained infamy in the mountaineering world. Not because he survived, sued his doctor, and walked away with an undisclosed settlement, but because it raised the veil on alpinism’s complicated relationship with performance-enhancing drugs.

High-altitude climbers have long used substances banned by the World Anti-Doping Code—everything from amphetamines to steroids to acclimatization aid acetazolamide, or Diamox, which prevents acute mountain sickness. The erectile-dysfunction drugs Viagra and Cialis are also common, since they decrease pulmonary-artery pressure, and if you talk to enough people you’ll hear rumors about climbers using EPO, the red-blood-cell booster popular with pro cyclists. Yet, due to the unique health challenges at altitude, the line between staying safe and getting a leg up has always been blurry.

Not counting Diamox, which carries minimal risk, dex is by far the most popular mountaineering drug. Banned by the World Anti-Doping Agency (WADA) but endorsed as a high-altitude rescue tool by the Wilderness Medical Society, dex works like most cortico-steroids, supplying synthetic cortisol to the body and suppressing inflammation. In the brain it stabilizes cell membranes, preventing fluid from leaking out of blood vessels into the surrounding tissue.

I’ve had highly paid, sponsored climbers and guides—people whose names you’d know right away—ask me about dex.

Because it inhibits cerebral swelling, dex is a terrific life rope for climbers who start to show signs of edema. It’s most often taken in pill form, but it can also be injected during emergencies. High-altitude doctors refer to it as a magic bullet, and some Spanish-speaking mountaineers have taken to calling it levanta muertos, because, as Argentine guide Damian Benegas says, “it brings life to a dead person.” The most famous case of this occurred during the 1996 Everest disaster, when Beck Weathers rose from a comatose state after Alpine Ascents guide Pete Athans gave him dex.

Over the past two decades, climbers have discovered that dex also works magic on the way up, increasing lucidity and triggering feelings of euphoria. This is where the trouble starts, because people who take cortico-steroids for more than a week impair their immune systems: adrenal glands that naturally produce cortisol are essentially shut off by the drug and stop responding to stress. As a result, wounds don’t heal quickly, and users are susceptible to infection. Emotional swings are also common after prolonged use, though doctors still don’t understand the precise mechanism for that.

Many in the medical community argue that dex should be employed only in life-threatening scenarios, since prophylactic use masks HACE symptoms and reduces the drug’s efficacy in the event of emergency. “You basically take away your safety rope by using it on the way up,” says Dr. Luanne Freer, the 55-year-old founder of the Everest ER clinic. “If you get stuck in a storm, then we have nothing to give you as a rescue drug.” Adds leading dex expert Dr. Robert “Brownie” Schoene, of Berkeley, California, “It is probably the one drug that has been abused in terms of enhancing mountaineering performance.”

This is due in part to how easy it is to obtain. You can fill a prescription at any pharmacy (Easterling’s source: Target) or buy it on the street in Nepal for five cents a dose. And demand is on the rise as Everest clients dishing out $70,000 per climb look to increase their odds of summiting. According to Bill Allen, co-owner of the Colorado outfitter Mountain Trip, half of his clients ask about dex before setting out for Everest. Johnson, the Everest ER doctor who treated Easterling, says, “I would be shocked if 50 percent of Everest climbers aren’t using dex at Camp III and above.” And not just clients: “I’ve had highly paid, sponsored climbers and guides—people whose names you’d know right away—ask me about dex. They don’t want their clients or anyone else to know they’re using it.”

One of the most high-profile episodes of alleged dexamethasone use in recent years occurred not with an amateur like Easterling but with a team of elite expedition climbers. On May 21, 2011, nine Spanish mountaineers summited 27,940-foot Lhotse, a neighbor of Everest and the world’s fourth-tallest peak. Three of them got into trouble on the descent and required a large-scale rescue that cost four other expeditions approximately $30,000, which was never repaid. According to Darío Rodríguez, a Spanish journalist who was in Everest Base Camp during the incident, only two of the climbers were using canisters of supplemental oxygen, which all but the hardiest alpinists rely on above 26,000 feet. But in the wake of the rescue, a rumor spread through Base Camp that at least one of the Spaniards who’d eschewed oxygen, Carlos Pauner, had been using a different aid on the way up: dex.

Pauner fared better than some—he was able to descend to Base Camp, while one of his teammates, Manuel González, had to be rescued after getting lost on the way down. Another climber who was not on Pauner’s team, Roberto Rodrigo, was medevaced from Camp II and lost 18 digits to frostbite. Some rescuers were furious. “They become so strong-minded about no oxygen, no oxygen,” says Damian Benegas, who assisted in the rescue along with his brother, Willie, “but they use dex. And I think that’s crap.”

Whether any of the climbers in fact used dex as an aid remains uncertain, but at least one doctor who was on the mountain believes it happened. Monica Piris, a 38-year-old Spanish emergency physician, was in Base Camp on May 21 when she received a radio call from a member of Pauner’s team who was suffering from HACE symptoms. “I told him that he should take 250 milligrams of Diamox and 8 milligrams of dexamethasone, use oxygen, stop his ascent, and come down immediately,” says Piris, who wouldn’t divulge the climber’s name. “He said that he would not use oxygen and that he would not stop his ascent but that he would take the medication, and as far as I know, that is what he did.”

In an email, Pauner denied using dex on the ascent but acknowledged taking it on the way down, once he “felt the onset of mountain sickness.” He also said that the Benegas brothers overdramatized the incident. “They saved the life of a member of my expedition, Manuel González, and for this we will always be thankful,” he wrote. “But that’s it. As for the rest of us in the expedition, we ascended and descended on our own effort and without requiring any of their assistance. The Benegas brothers tend to exaggerate everything to their own benefit, acting as though they are heroes.

Amphetamines were the first drug of choice in the mountains. In 1953, Austria’s Hermann Buhl took pervitin, the superdrug that Nazi troops took before battle, during his solo first ascent of Pakistan’s Nanga Parbat. Ten years later, during his historic 1963 traverse of Everest, American climber Tom Hornbein gave two teammates, Lute Jerstad and Barry Bishop, dexedrine to aid their descent. “My impression is it didn’t do a damn bit of good,” says Hornbein, who didn’t take the speed himself.

Steroids hit the scene shortly after. Seeking a way to treat severe mountain sickness, the Indian army began giving soldiers a corticosteroid called betamethasone, similar to dexamethasone, in the late '60s. In 1974, a young American doctor named Peter Hackett read about their positive results in the New England Journal of Medicine. At the time, Hackett was trekking around Nepal and looking to start a career in high-altitude medicine. The following spring, while working for the Himalayan Rescue Association, he started injecting HACE-afflicted climbers with corticosteroids, including dex. “I only used them for people who were unconscious or severely ill,” says Hackett, now the director of the Telluride, Colorado–based Institute for Altitude Medicine. “I wish I’d had the idea to use them for people who weren’t so bad off, because I would’ve seen miraculous results. But once somebody’s unconscious, it’s really not that effective. I think it helped, but it was hard to tell.”

Clients like Easterling can hire personal climbing Sherpas a la carte.

In the early '90s, Hackett started endorsing dex to prevent altitude sickness, particularly on summit day. “I became more convinced that [taking dex on summit day] was worth considering,” says Hackett, who has advised many major international outfitters, “as I witnessed more and more folks getting into trouble and dying from altitude issues—even with reasonable rates of ascent.” His opinion hasn’t changed: “I tell guides, ‘If your clients want to take dex on the way up, they’re the ones you have to worry less about. They’ll probably do better and go faster than the others.’” But he stops short of explicitly recommending it. “I don’t want to be known as a drug pusher,” he says.

Some find this sort of hedged endorsement troublesome. “What worries me about Peter’s [stance] is, why are guides encouraging this?” argues David Hillebrandt, a British doctor and president of the International Mountaineering and Climbing Federation’s medical commission. “That’s professionals encouraging drug use in the mountains.” Hackett’s response to detractors: “I think anybody that just automatically [decries] any kind of altitude-adjustment medicine on the basis that it’s unsporting, they belong in the medieval ages.”

Nowadays, many outfitters allow their clients to use dex on summit day. “If somebody has had it prescribed by a reputable mountaineering doctor, then I’m not going to tell them they shouldn’t take it,” says Mountain Trip’s Allen, who is advised by Hackett. New Zealand-based Adventure Consultants doesn’t recommend the drug but doesn’t have a policy against it. Another leading guide, Russell Brice, of Himalayan Experience, says no clients have asked permission to use dex—but that if they did, he “would not allow it.” Seattle-based outfitter Alpine Ascents forbids clients from using it as an aid. “It’s a written protocol for us,” says Todd Burleson, the company’s owner.

Easterling’s outfitter, Asian Trekking, has no such scruples. The Kathmandu-based group has a spotty reputation on Everest, thanks in part to a couple of recent high-profile client deaths, including German doctor Eberhard Schaaf, who is believed to have succumbed to cerebral edema during a traffic jam on the mountain last May. According to two of Schaaf’s teammates, the doctor was taking dex during his ascent to treat a sinus infection. Most Western outfitters select their clients far in advance and form a relationship with them in the months leading up to the expedition; Asian Trekking, on the other hand, simply offers support services—a permit, tents, food, and oxygen in Base Camp and beyond. Clients like Easterling can hire personal climbing Sherpas a la carte.

“Nobody wants to be known as a climber who got up with the aid of drugs.” Says Freer, “They know they’ll have a target on their backs in Base Camp if other people find out.”

A fitness freak who grew up wrestling in rural Virginia, Easterling had summited Mount Rainier and Denali but had never climbed in the Himalayas. He found Asian Trekking on the Internet and signed up 30 days before he left for Nepal. He also trained obsessively, climbing stairs for three hours a day, six days a week, while wearing two 20-pound vests. The mission was personal: he claims to have been saved by God in 2004 and wanted to place a cross on top of the world. “For some reason it was very clear,” says Easterling. “I was supposed to climb Everest.”

So how did such a strong and driven amateur climber end up popping dex like Skittles? Simple: he trusted his doctor. Perhaps the biggest wild card in climbing’s health-and-safety conversation is that doctors don’t need special training to prescribe high-altitude medications. Before leaving, Easterling read up on dex’s benefits, scheduled an appointment with Dr. Tang, and asked about the drug. Tang looked it up on eMedicine, the online drug database. According to the doctor’s testimony, he instructed Easterling to start taking dex the moment he “felt short of breath upon exertion”—which is exactly what Easterling did when he arrived in Lukla.

Dex is largely a behind-tent-walls phenomenon. According to George Dunn, co-owner of International Mountain Guides, “Nobody wants to be known as a climber who got up with the aid of drugs.” Says Freer, “They know they’ll have a target on their backs in Base Camp if other people find out.” I spoke with more than 50 climbers, doctors, and guides, and none agreed to name any dex users. But almost all claimed to know some.

So who does it? Mountain Trip co-owner Bill Allen, veteran 8,000-meter-peak guide Adrian Ballinger, and Schoene, the Berkeley high-altitude doctor, all told me they’d used dexamethasone prophylactically. So did climber and photographer Cory Richards, who took the drug in 2010 to climb Lhotse and says he has “no regrets.” Richards says he didn’t take dex on his 2011 winter ascent of Pakistan’s Gasherbrum II, when he and his two partners survived a monster avalanche, or last year on Everest, when he was medevaced out before attempting a summit bid.

Pete Athans, who has summited Everest seven times and guided commercial trips for Alpine Ascents for more than 20 years, took dex on a handful of occasions in the mid-'90s, mostly above 25,000 feet, when he experienced painful headaches. “Not having a headache when you’ve had a really debilitating one makes you feel really good,” says Athans. “It’s like knocking your head against the wall and finally stopping. But it also has an amphetamine effect. It just kind of gives you a little shot in the arm.”

In 1994, during a raging five-day windstorm that pinned his team on Everest at 26,000 feet, Burleson, the Alpine Ascents owner, downed dex the entire time in order to preserve oxygen stores for clients. He finally summited on the fifth day. “It worked unbelievably well,” says Burleson. “But that was an intense-environment situation. If I were going to climb Everest tomorrow, I would not be taking it prophylactically.”

The list of Himalayan stars who say they haven’t used dex as an ascent aid is much longer: seven-time Everest summiter Ed Viesturs; renowned North Face expedition leader Conrad Anker; Italian alpinist Simone Moro and Kazakhstani Denis Urubko, who summited G2 with Richards in 2011; Swiss speed climber Ueli Steck; Spain’s Edurne Pasaban, the first woman to climb all 14 8,000-meter peaks; expedition photographer and climber Jimmy Chin; Brice, the Himalayan Experience founder; four-time Everest summiter Melissa Arnot; and veteran Everest guide and Outside correspondent Dave Hahn, to name a few. Still, most of those climbers carry the drug in their med kits in case of emergency. As Hahn puts it, “They’re your fingers, they’re your toes, it’s your nose, you know?”

The use of drugs is such a sensitive subject partly because the sport has always placed a high value on purity. Its icons—Hillary, Messner, Viesturs, Anker—are seen in an almost holy light. When I asked Steve House, a modern Himalayan giant, about doping, he simply said, “Any performance enhancer runs counter to the spirit of climbing.”

Reinhold Messner, who famously took nothing more than aspirin when setting records on the world’s highest peaks in the '70s and '80s, compares using drugs in general, and dex in particular, to placing bolts in the rock. “It’s not possible anymore to tell who is doing great things in the Himalayas and who is using drugs and cheating,” he told me. “It’s a form of cheating, clearly. You cheat yourself and you cheat others by using drugs.”

If somebody wants to use, what can you do? Do you have somebody at the bottom of every mountain taking urine samples? When they come off, you say, ‘OK, here, pee in the cup’? It’s never going to happen.

More than anyone, Messner was responsible for creating the image of the proud, pure climber, thanks to his groundbreaking oxygen-free ascents on 8,000-meter peaks. These days the few climbers who don’t use oxygen, like House and German ski mountaineer Benedikt Böhm, are viewed as the sport’s standard-bearers. Some European climbers and doctors want even supplemental oxygen, which WADA removed from its list of banned substances in 2010, to be deemed doping—even though only about 60 climbers have summited Everest without it.

Although dex is rarely used in lieu of oxygen, it’s not unheard of. Chad Kellogg, a speed climber from Seattle, acknowledges taking one pill of dex during a 2010 attempt to break Frenchman Marc Batard’s oxygen-free speed record up and down Everest—“not as an aid,” he says, “but as a preventative.” His attempt failed.

In the wake of Easterling’s episode and the Lhotse rescue, the sport’s gatekeepers are looking to crack down. The International Mountaineering and Climbing Federation—which governs competitive sport climbing and strives to preserve the “spirit and traditions” of alpinism—is working on a report about drug use in the mountains. But the organization has no regulatory power and doesn’t enforce any WADA regulations in mountaineering. The fact remains that on the world’s tallest peaks, there are no rules.

“We’re not racing, there’s no competition, it’s not on TV,” says Viesturs. “If somebody wants to use, what can you do? Do you have somebody at the bottom of every mountain taking urine samples? When they come off, you say, ‘OK, here, pee in the cup’? It’s never going to happen.”

On a warm night last September, I met Easterling and his lawyer, Mike Maxwell, for Thai food in a small Seattle suburb. It was the first time Easterling had spoken with the press since his Everest meltdown. If I didn’t know that his body had been ravaged by steroids, it would have been impossible to tell. He looked like the wrestler he was back in Virginia, thick and lean, with a buzz cut and an easy grin. His arms bulged out of his T-shirt, and veins popped from his neck—results of his recent return to weight lifting, he said. Only when he shoveled a forkful of pad Thai toward his mouth did I notice anything strange. His hand shook so much that some of the food dropped to his plate.

“Is that from the dex?” I asked.

“Yeah,” he said.

He got quiet for a moment and then launched into a story that was hard to fathom. Going into his Everest expedition, Easterling was an even-keeled insurance salesman with a heavy faith. “I was very stable, very calm, no temper,” he said. Upon his return, and in the months that followed, he became so volatile that Washington’s Adult Protective Services agency appointed someone to take care of him for a year. Clinical depression set in; acne covered his entire body. Washing the sores was too painful. “There was a month when I literally did not bathe once,” he said.

His doctors put him on 10 milligrams of Xanax per day, essentially turning him into a zombie. Even when he could function, panic attacks paralyzed him. Getting off dex, he said, “was like sticking my finger in an electric socket. My whole nervous system was fried.”

Easterling told me that the only reason he agreed to be interviewed was to warn others: “People need to know dex can kill you.”

When I had discussed Easterling’s case with other climbers, many questioned how he could have been so unaware of the drug’s dangers. I asked Easterling about it, and he reiterated that he simply trusted his doctor. “He was very confident when he gave the prescriptions,” Easterling recalled. Dr. Tang did not respond to interview requests, but in 2010 he told a King County Superior Court that he did nothing wrong, testifying: “The only thing I recall was the patient came in, he says he’s climbing Mount Everest, that he would need medication to treat high-altitude sickness, such as acute mountain sickness, pulmonary edema, and cerebral edema. And after looking at my source”—eMedicine—“I agreed with him.... [Dexamethasone] was only an as-needed medication.”

Easterling’s Asian Trekking guides asked what medications he brought but never the quantity. “They don’t ask, ‘Are you going to be taking dexamethasone the whole trip?’” he said. Still, he never pursued legal action against the outfitter.

Easterling told me that the only reason he agreed to be interviewed was to warn others: “People need to know dex can kill you.”

The day after our dinner, Easterling flew to Thailand to start over at age 30. He hoped to connect with a Christian missionary group he’d heard about and settle into a new routine. But after just two months he flew back to Seattle. He was addicted to his meds and needed a new prescription from his doctors. In January he told me that he hoped to return to Thailand in the spring to give the missionary work another shot.

“I’m trying to integrate myself back into normal life,” he said. “I’m still working on that. I cherish the good days, I really do. I like to think they’re increasing.”

Devon O'Neil wrote about crisis-response group Global Rescue in April 2011.