IN 1962 Kupperman and Epstein1suggested that medroxyprogesterone acetate (MPA) may be useful in the treatment of idiopathic isosexual precocity in infants and children. This agent was selected over other hormonal inhibitors of gonadotropin secretion because it apparently had no androgenic or estrogenic potential. After treating five girls with idiopathic isosexual precocity for periods of 4 to 14 months with a long-acting preparation (Depo-Provera), they reported their preliminary observations that use of MPA had arrested menstruation, reduced the cornification of the basal cells of the vaginal epithelium, and diminished mammary growth. In two boys with the syndrome, spermatogenesis was apparently arrested and the excretion of 17-ketosteroids was diminished following treatment. The question as to whether the treatment had modified the rate of linear growth or rate of epiphyseal maturation could not be resolved by their study, which was limited in the number of patients studied and in its duration.