A minority of individuals with mental retardation engage in offensive sexual behavior (e.g., child molestation, genital exposure, rape). Many of these individuals may benefit from the adjunctive administration of antilibidinal drugs. The two most widely used are the antiandrogens, medroxyprogesterone acetate (MPA) and cyproterone acetate (CPA). In the present paper the efficacy, cautions, side effects, and mode(s) of action of these substances were reviewed and medico-legal issues surrounding their use discussed. Controlled studies of antilibidinal agents with adequate numbers of patients using clearly defined (e.g., cognitive abilities) and valid and reliable outcome measures are needed.