A commonly repeated notion is that Hitler had only one testicle, an assertion made in the autopsy report filed by Soviet pathologists who examined bodies removed from shallow graves in a garden near Hitler's bunker, including one the Russians concluded was Hitler's. Various historians have either accepted this finding or rejected it as an attempt by the Bolsheviks to portray Hitler as sexually defective. Dr. Redlich remains neutral on this question, though he points out that monorchism, as the condition is called, is sometimes associated with hypospadia. And there is no evidence, the author writes, to show that Hitler had syphilis, despite persistent rumors that he contracted the disease from a Jewish prostitute.

Hitler's personal physician, Dr. Morell, to whom the Nazi leader was devoted, has always been controversial figure. Some biographers have deemed him a charlatan and an exploiter. Others have said that he deliberately tried to harm his patient. Dr. Redlich concludes, in contrast, that while Dr. Morell was ignorant and made mistakes -- at one point he gave Hitler both very potent laxatives and opiates, a dangerous combination -- he ''was proud of his historical role,'' enjoyed the perquisites it provided and never caused deliberate harm.

Was Hitler a drug addict? Dr. Redlich thinks not. Dr. Morell did prescribe amphetamines for Hitler, but this was a common practice at the time, the author says. ''I think he took drugs, but he did not become addicted,'' Dr. Redlich said in an interview. ''And when he realized they were harmful, he stopped.'' He added that Hitler was a teetotaler, and fiercely opposed to the use of nicotine.

In the end, Dr. Redlich concludes that ''Hitler's crimes and errors were not caused by illness.''

Hitler scholars who have reviewed the new book said they were impressed with the scope and detail of the author's research. Dr. Ian Kershaw, a history professor at the University of Sheffield in England, whose own biography, ''Hitler 1889-1936: Hubris'' (W. W.Norton, $35) will be published in January, has called the book ''the most thorough investigation yet undertaken of Hitler's medical condition.'' Dr. John Lukacs, a retired historian and author of ''The Hitler of History'' (Knopf, $25.50), calls Dr. Redlich's work ''a great contribution.''

Yet the psychiatrist does not limit himself to a discussion of Hitler's physical self. In the last section of the book, he goes beyond that, delving into the Nazi leader's psyche and constructing what amounts to a psychiatric profile.

Psychoanalyzing Hitler has been a popular endeavor ever since the United States Government's Office of Strategic Services commissioned a psychological profile of Hitler in hope of finding novel ways to defeat him. After Hitler's death, efforts to explain his behavior in psychological terms proliferated. Among them are Rudolph Binion's 1976 biography, ''Hitler Among the Germans'' (Northern Illinois University Press), which traces Hitler's aggression to his rage at his mother's doctor, and Robert Waite's ''The Psychopathic God: Adolf Hitler'' (Da Capo Press; $16.95), which concluded that Hitler was sexually perverse.

Indeed, Dr. William McKinley Runyan, a professor in the school of social welfare at the University of California at Berkeley, said Nazi Germany became, in a sense, ''a test case'' for the budding genre of psycho-history. ''Most people who write about psychohistory end up writing about the Nazi era,'' Dr. Runyan said.