In the early 1960s, Neumann and his colleagues in West Berlin, working experimentally with rats, discovered the antiandrogenic properties of cyproterone and cyproterone acetate (Neumann, Elger, Steinbeck and von Berswordt-Wallrabe, 1968). Shortly thereafter, clinical application of the new drug to human beings was begun investigatively on a small scale in selected clinics in West Germany and Switzerland (Laschet et al., 1967; Koffet, 1968; Seebandt, 1968). Among the patients chosen for treatment were sex offenders, that is men whose self-regulation of publicly and legally unacceptable sexual behavior was so severely impaired that their only alternative was long-term incarceration. In a parallel investigation with another drug, methyloestrenolone (19-nor- 17a-methyltestosterone), Servais (1968) in Belgium also obtained therapeutic results. See also Hubin and Servais (1968). In women the drug has an antiovulatory effect. In the United States at that time, as now, cyproterone was not released by the Federal bureaucracy of the Food and Drug Administration (FDA) for behavioral research. It has been possible, however, to substitute medroxyprogesterone acetate (Provera?, Upjohn), a synthetic steroid most widely known for its progestinic effect, but known also to have a counteractive effect on the sex hormones in cases of idiopathic sexual precocity. Claude Migeon, M.D. and his assistant Marco Rivrola, M.D., and I made a decision to try therapy with Depo-Provera? when a bisexual transvestite patient under long-term followup study underwent a crisis of pedophilia, fellatio and incest with his six year old son (Money, 1969; and Case Illustration, below). * Supported in Research by Grant ?HD-00325 and Research Career Development Award #HD-K3-18,635, United States Public Health Service. I also wish to acknowledge the assistance of Mr. Ronald J. Gaskin in the abstracting of case histories and the preparation Table 1. The material of this paper will appear in The Treatment of the Sexual Offender (H. L. P. Resnick and M. Wolfgang, eds.), Boston, Little Brown. In press.