239 women received medroxyprogesterone during their pregnancies; they received no other hormone therapy. Of the 203 who went to term 172 were treated prior to the 12th week; the latter are discussed. Average daily dose varied from 5-50 mg or more orally with or without injectable supplements. Sex distribution of infants was 92 male to 82 female there were 2 sets of twins 1 stillborn and 1 newborn with congenital heart disease. The authors report a case of transient masculization of a female infant born with an enlarged clitoris which persisted until age 6 months. Masculization of the female fetus may occur if the fetus is subjected to some source of androgen prior to the 12th week of gestation after which the female generative tract is well differentiated and not likely to be affected. Other studies have reported up to 18% masculization using exogenous hormones with abnormalities as extreme as labial fusion and cloacal formation necessitating surgical correction.