FROM THE BEGINNING, DR. LI Zhisui realized that his new patient was going to be a difficult case. Their first meal together, taken in April 1955 at a grand residence in Beijing’s Forbidden City, was a caloric nightmare of fatty pork and lamb, as well as fish and vegetables swimming in cooking oils. At one point, Dr. Li even felt obliged to chide his host for his habit of chain-smoking English cigarettes. But Mao Zedong, absolute ruler of China and terminally incorrigible Bad Boy, brushed aside those concerns with a joke. “Smoking,” replied the portly tyrant, then 61, “is also a deep-breathing exercise, don’t you think?”

For the next 22 years as Mao’s personal physician, Li often found himself privy to some of the chairman’s deepest secrets. Now the doctor, who emigrated to the U.S. six years ago, has produced what may be the ultimate tell-all biography—the 638-page Private Life of Chairman Mao—which includes everything from details about the dictator’s addiction to sleeping pills to his unusual standards of personal hygiene. “Mao’s way of thought and doing things—eating, sex, sleep—were not those of a normal man,” says Li, now 74. “He was a very queer person.”

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Eccentric, at any rate. In matters of personal care, for instance, Mao was strictly a minimalist. When Li first started treating him, he was startled to discover that the chairman had apparently never brushed his teeth. Instead, as with many Chinese peasants, he rinsed his mouth with tea, then chewed the leaves. The result was that Mao’s teeth were green and his gums oozed pus from infections. Li encouraged the Great Helmsman to brush, without much success. “Does a tiger brush his teeth?” Mao demanded.

Perhaps not. But they do occasionally bathe, another practice that Mao considered “a waste of time.” Aside from his periodic swims, the closest he came to cleansing his body was when he received rubdowns with hot towels. Again, explains Li, this was traceable to Mao’s peasant background (though he didn’t come from a dirt-poor family). “These people have a three-bath philosophy,” says Li. “A bath at birth, one before marriage and one at death.”

Although China may have projected a puritanical image to the world, in matters of sex, Mao was the equal of the legendary Yellow Emperor, who was famous for deflowering 1,000 virgins. In line with Daoist philosophy, he believed that the more women he slept with, the longer he would live. (Mao fathered at least six children by four wives.) Thus he was an almost compulsive womanizer, sometimes bedding three, four and five partners at a time. Given the chairman’s godlike status among the Chinese people, recalls Li, it never took any coaxing to scare up willing young partners. Many were recruited during the ballroom “dance parties,” which were supposedly proscribed by the government as decadent, that Mao liked to throw at his palace to burn off his restless energy. Unfortunately for his groupies, Mao was not a considerate lover. Several young women contracted a minor venereal disease. Mao, who had no symptoms, was identified as the carrier but refused to take any medication to cure the ailment. “Why are you getting so excited,” he told Li. “If it doesn’t bother me, it doesn’t matter.”

All this left Li profoundly disillusioned. Descended from a long line of doctors (his great-grandfather had been a physician to the Empress Dowager Cixi), Li was born in Beijing and trained at American-run medical schools. He and his future wife, Lillian, the daughter of a prosperous landlord, both grew up speaking fluent English. During the Chinese civil war in the 1940s, he worked as a ship’s surgeon out of Sydney. Following the triumph of the Communists in 1949, Li and his wife returned to Beijing filled with idealism and eager to help rebuild their country. Before long, by dint of his training and ability, Li came to the attention of top government officials, who tapped him to become Mao’s doctor.

Li admits that he was able to flourish in his post by exhibiting total loyalty to Mao despite his increasing disenchantment with the chairman’s ruthlessness. “I kept silent, and I kept out of politics,” he says. “I was cautious in every way.” Doctor and patient even became friends of a sort. The chairman suffered from severe insomnia, and late at night he would often summon Li for long bull sessions. “Mao had no friends, and his only entertainment was sex,” says Li. “I was able to give him English lessons and to listen to his discourses on history and philosophy.”

Perhaps Li’s greatest medical feat was to get Mao ready for his 1972 meeting with President Nixon. As the summit approached, the 79-year-old chairman fell gravely ill, suffering from pneumonia, congestive heart disease and swelling of his internal organs. Typically, he refused all treatment until three weeks before the summit. At that point Li was able to impose a regimen of antibiotics and other measures that restored Mao’s health enough to allow the historic encounter to take place. Four years later, Li was at his side when the chairman finally died of heart failure and amyotrophic lateral sclerosis—Lou Gehrig’s disease. His last act as Mao’s physician was to prepare the embalming process that was supposed to preserve the leader forever.

Li left China for good in 1988 with Lillian, who was suffering from kidney trouble, and joined their sons, Chong, now 44, and Erchong, 37, and daughter-in-law Mei, 34, near Chicago. His decision to set down his account of Mao’s private life did not come easily. First, there was the problem of his archives. During the populist upheaval of the Cultural Revolution in the 1960s, Li had destroyed the 40 notebooks of his private diary out of fear that they would be uncovered and used against him. All he could reconstruct was 20 volumes of notes. He found, however, that many of the crucial episodes came back to him clearly. “For 22 years my life depended on what Mao said,” says Li. “His words were burned into my mind.” Above all, he was motivated by the debt he felt he owed to Lillian, who died of kidney failure in 1989. “In her last days in the hospital, before she slipped into a coma,” says Li, “she urged me to write this book as a record for our children, grandchildren and the generations to follow.”

Li now lives with his son Erchong and his family, caring for his 4-year-old grandson Alan. Next month he is scheduled to become an American citizen. Yet the chairman’s impact on his life is something that he still cannot shake. “I would like to have my beloved wife appear in my dreams, but these days I only dream of Mao,” says Li. “I always wake up and have to walk around the room to calm down.” Li fears reprisals from the Chinese government over the publication of The Private Life of Chairman Mao. But he sees the work as a means of redemption for having lent his skills, however unwillingly, in the service of a monster. “Even if they kill me,” he says, “my book will live on.”