Milton Diamond graduated from the City College of New York with a B.S. in biophysics in 1955, after which he spent three years in the Army as an engineering officer, stationed in Japan. On returning to the United States, he attended graduate school at University of Kansas from 1958–1962 and earned a Ph.D. in anatomy and psychology from that University. His first job was teaching at the University of Louisville, School of Medicine where he simultaneously completed two years toward an M.D., passing his Basic Medicine Boards, and in 1967 he moved to Hawaii to take up a post at the recently established John A. Burns School of Medicine. Milton Diamond had a long running feud with the psychologist Dr. John Money. In the early seventies, Diamond and Money were attending a conference on transgenderism in Dubrovnik. According to the book As Nature Made Him: The Boy Raised As a Girl at this conference Money initiated a loud and aggressive argument with Diamond. One witness claims that Money punched Diamond; however, Diamond himself said that he could not recall any physical contact during this encounter.
Diamond is known for following up the case of David Reimer, a boy raised as a girl after a botched circumcision, which had been performed using an unconventional method of electrocauterization, rather than more typical methods using a clamp and scalpel, causing his penis to be burned beyond surgical repair. This case, which Diamond renamed that of "John/Joan" to protect Reimer's privacy, has become one of the most cited cases in the literature of psychiatry, anthropology, women's studies, child development, and biology of gender. With the cooperation of H. Keith Sigmundson, who had been Reimer's supervising psychiatrist, Diamond tracked down the adult Reimer and found that John Money’s sex reassignment of Reimer had failed. Diamond was the first to alert physicians that the model, proposed by Reimer's case, of how to treat infants with intersex conditions was faulty. Diamond recommended that physicians do no surgery on intersexed infants without their informed consent, assign such infants in the gender to which they will probably best adjust, and refrain from adding shame, stigma and secrecy to the issue, by assisting intersexual people to meet and associate with others of like condition. Diamond similarly encouraged considering the intersex condition as a difference of sex development, not as a disorder.
Work, appointments and awards
Diamond wrote extensively about abortion and family planning, pornography, intersexuality, transsexuality, and other sex- and reproduction-related issues for professional sex and legal journals, as well as lay periodicals. He was frequently interviewed for public media and legal matters, and often served as an expert in court proceedings, and was known for his research on the origins and development of sexual identity. He retired from teaching in 2009, but continued to research and consult concerning transsexuality, intersexuality and pornography until he retired fully in 2018.
