Evil scares us. Arguably our best horror stories, the ones that give us nightmares, are about evil people doing evil things—especially evil experiments. The Island of Dr. Moreau by H.G. Wells is a classic that comes to mind. In modern cinema, movies like The Human Centipede continue that gruesome tradition. But these are fictional. The truth is that we need only look at recent human history to find real, live, utterly repugnant evil. Worse yet, it is evil perpetrated by doctors.

Here are 10 of the most evil experiments ever performed on human beings—black and other people of color, women, prisoners, children and gay people have been the predominant victims.

1. The Tuskegee Experiments

There's a good reason many African Americans are wary of the good intentions of government and the medical estblishment. Even today, many believe the conspiracy theory that AIDS, which ravaged the African-American community, both gay and straight, was created by the government to wipe out African Americans. What happened in Tuskegee, Alabama in 1932 is one explanation for these fears.

At the time, treatments for syphilis, a sexually transmitted disease that causes pain, insanity and ultimately, death, were mostly toxic and ineffective (things like mercury, which caused, kidney failure, mouth ulcers, tooth loss, insanity, and death). Government-funded doctors decided it would be interesting to see if no treatment at all was better than the treatments they were using. So began the Tuskegee experiments.

Over the course of the next 40 years, the Tuskegee Study of Untreated Syphilis in the Negro Male denied treatment to 399 syphilitic patients, most of them poor, black, illiterate sharecroppers. Even after penicillin emerged as an effective treatment in 1947, these patients, who were not told they had syphilis, but were informed they suffered from “bad blood,” were denied treatment, or given fake placebo treatments. By the end of the study, in 1972, only 74 of the subjects were still alive. Twenty eight patients died directly from syphilis, 100 died from complications related to syphilis, 40 of the patients' wives were infected with syphilis, and 19 children were born with congenital syphilis.

2. The Aversion Project

They didn’t like gay people in apartheid-era South Africa. Especially in the armed forces. How they got rid of them is shocking. Using army psychiatrists and military chaplains, who were, presumably privy to private, “confidential” confessions, the apartheid regime flushed out homosexuals in the armed forces. But it did not evict them from the military. The homosexual “undesirables” were sent to a military hospital near Pretoria, to a place called Ward 22 (which in itself sounds terrifying).

There, between 1971 and 1989, many victims were submitted to chemical castrations and electric shock treatment, meant to cure them of their homosexual “condition.” As many as 900 homosexuals, mostly 16-24 years old who had been drafted and had not voluntarily joined the military, were subjected to forced “sexual reassignment” surgeries. Men were surgically turned into women against their will, then cast out into the world, the gender reassignment often incomplete, and without the means to pay for expensive hormones to maintain their new sexual identities.

The head of this project, Dr. Aubrey Levin, went on to become a clinical professor at the University of Calgary. That is until 2010, when his license was suspended for making sexual advances towards a male student. He was sentenced to five years in prison for other sexual assaults (against males).

3. Guatemalan STD Study

Syphilis seemed to bring out the inherent racism in government-funded doctors in the 1940s. Tuskegee's black people weren’t the only victims of morally reprehensible studies of this disease. Turns out Guatemalans were also deemed suitable unknowing guinea pigs by the U.S. government.

Penicillin having emerged as a cure for syphilis in 1947, the government decided to see just how effective it was. The way to do this, the government decided, was to turn syphilitic prostitutes loose on Guatemalan prison inmates, mental patients and soldiers, none of whom consented to be subjects of an experiment. If actual sex didn’t infect the subject, then surreptitious inoculation did the trick. Once infected, the victim was given penicillin to see if it worked. Or not given penicillin, just to see what happened, apparently. About a third of the approximately 1,500 victims fell into the latter group. More than 80 “participants” in the experiment died.

The Guatemalan study was led by John Charles Cutler, who subsequently participated in the later stages of Tuskegee. In 2010, Secretary of State Hillary Clinton formally apologized to Guatemala for this dark chapter in American history.

4. Agent Orange Experiments

Prisoners, like people of color, have often been the unwilling objects of evil experiments. From 1965 to 1966, Dr. Albert Kligman, funded by Dow Chemical, Johnson & Johnson, and the U.S. Army, conducted what was deemed “dermatological research” on approximately 75 prisoners. What was actually being studied was the effects of Agent Orange on humans.

Prisoners were injected with dioxin (a toxic byproduct of Agent Orange)—468 times the amount the study originally called for. The results were prisoners with volcanic eruptions of chloracne (severe acne combined with blackheads, cysts, pustules, and other really bad stuff) on the face, armpits and groin. Long after the experiments ended, prisoners continued to suffer from the effects of the exposure. Dr. Kligman, apparently very enthusiastic about the study, was quoted as saying, “All I saw before me were acres of skin… It was like a farmer seeing a fertile field for the first time.” Kligman went on to become the doctor behind Retin-A, a major treatment for acne.

5. Irradiation of Black Cancer Patients

During the Cold War, the U.S. and the Soviet Union spent much of their time trying to figure out if they could survive a nuclear catastrophe. How much radiation could a human body take? This would be important information for the Pentagon to know, in order to protect its soldiers in the event they were crazy enough to start an atomic holocaust. Enter the seeming go-to government choice for secret experimentation: unknowing African Americans.

From 1960 until 1971, Dr. Eugene Saenger, a radiologist at the University of Cincinnati, led an experiment exposing 88 cancer patients, poor and mostly black, to whole body radiation, even though this sort of treatment had already been pretty well discredited for the types of cancer these patients had. They were not asked to sign consent forms, nor were they told the Pentagon funded the study. They were simply told they would be getting a treatment that might help them. Patients were exposed, in the period of one hour, to the equivalent of about 20,000 x-rays worth of radiation. Nausea, vomiting, severe stomach pain, loss of appetite, and mental confusion were the results. A report in 1972 indicated that as many as a quarter of the patients died of radiation poisoning.

6. Slave Experiments

It should be no surprise that experiments were often conducted on human chattel during America’s shameful slavery history. The man considered the father of modern gynecology, J. Marion Sims, conducted numerous experiments on female slaves between 1845 and 1849. The women, afflicted with vesico-vaginal fistulas, a tear between the vagina and the bladder, suffered greatly from the condition and were incontinent, resulting in societal ostracism.

Because Sims felt the surgery was, “not painful enough to justify the trouble,” as he said in an 1857 lecture, the operations were done without anesthesia. Being slaves, the women had no say as to whether they wanted the procedures or not, and some were subjected to as many as 30 operations. There are many advocates for Dr. Sims, pointing out that the women would have been anxious for any possibility of curing their condition, and that anesthetics were new and unproven at the time. Nevertheless, it is telling that black slaves and not white women, who presumably would have been just as anxious, were the subjects of the experiments.

7. “The Chamber”

Back to the Cold War. Prisoners were again the victims, as the Soviet Secret Police conducted poison experiments in Soviet gulags. The Soviets hoped to develop a deadly poison gas that was tasteless and odorless. At the laboratory, known as “The Chamber," unknowing and unwilling prisoners were given preparations of mustard gas, ricin, digitoxin, and other concoctions, hidden in meals, beverages or given as “medication.” Presumably, many of these prisoners were not happy with their meals, although, being the gulag, records are spotty. The Secret Police apparently did finally come up with their dream poison, called C-2. According to witnesses, it caused actual physical changes (victims became shorter), and victims subsequently weakened and died within 15 minutes.

8. World War II: Heyday of Evil Experiments

While evil experiments may have been going on in the U.S. during World War II (Tuskegee, for example), it’s hard to argue that the Nazis and the Japanese are the indisputable kings of evil experimentation. The Germans, of course, conducted their well-known experiments on Jewish prisoners (and, to a much lesser extent, Romany people and homosexuals and Poles, among others) in their concentration/death camps. In 1942, the Luftwaffe submerged naked prisoners in ice water for up to three hours to study the effects of cold temperatures on human beings and to devise ways to rewarm them once subjected.

Other prisoners were subjected to streptococcus, tetanus and gas gangrene. Blood vessels were tied off to create artificial “battlefield” wounds. Wood shavings and glass particles were rubbed deep into the wounds to aggravate them. The goal was to test the effectiveness of sulfonamide, an antibacterial agent. Women were forcibly sterilized. More gruesomely, one woman had her breasts tied off with string to see how long it took for her breastfeeding child to die. She eventually killed her own child to stop the suffering. And there is the infamous Josef Mengele, whose experimental “expertise” was on twins. He injected various chemicals into twins, and even sewed two together to create conjoined twins. Mengele escaped to South America after the war and lived until his death in Brazil, never answering for his evil experiments.

Not to be outdone, the Japanese killed as many as 200,000 people during numerous experimental atrocities in both the Sino-Japanese War and WWII. Some of the experiments put the Nazis to shame. People were cut open and kept alive, without the assistance of anesthesia. Body limbs were amputated and sewn on other parts of the body. Limbs were frozen and then thawed, resulting in gangrene. Grenades and flame-throwers were tested on living humans. Various bacteria and diseases were purposely injected into prisoners to study the effects. Unit 731, led by Commander Shiro Ishii, conducted these experiments in the name of biological and chemical warfare research. Before Japan surrendered, in 1945, the Unit 731 lab was destroyed and the prisoners all executed. Ishii himself was never prosecuted for his evil experiments, and in fact was granted immunity by Douglas MacArthur in exchange for the information Ishii gained from the experiments.

9. The Monster Study

Add children to the list of vulnerable people subjected to evil experiments. In 1939, Wendell Johnson, University of Iowa speech pathologist, and his grad student Mary Tudor, conducted stuttering experiments on 22 non-stuttering orphan children. The children were split into two groups. One group was given positive speech therapy, praising them for their fluent speech. The unfortunate other group was given negative therapy, harshly criticizing them for any flaw in their speech abilities, labeling them stutterers.

The result of this cruel experiment was that children in the negative group, while not transforming into full-fledged stutterers, suffered negative psychological effects and several suffered from speech problems for the rest of their lives. Formerly normal children came out of the experiment, dubbed “The Monster Study,” anxious, withdrawn and silent. Several, as adults, eventually sued the University of Iowa, which settled the case in 2007.

10. Project 4.1

Project 4.1 was a medical study conducted on the natives of the Marshall Islands, who in 1952 were exposed to radiation fallout from the Castle Bravo nuclear test at Bikini Atoll, which inadvertently blew upwind to the nearby islands. Instead of informing the residents of the island of their exposure, and treating the victims while they studied them, the U.S. elected instead just to watch quietly and see what happened.

At first the effects were inconclusive. For the first 10 years, miscarriages and stillbirths increased but then returned to normal. Some children had developmental problems or stunted growth, but no conclusive pattern was detectable. After that first decade, though, a pattern did emerge, and it was ugly: Children with thyroid cancer significantly above what would be considered normal. By 1974, almost a third of exposed islanders developed tumors. A Department of Energy report stated that, “The dual purpose of what is now a DOE medical program has led to a view by the Marshallese that they were being used as ‘guinea pigs’ in a ‘radiation experiment.’”