Twelve women with congenital adrenal hyperplasia are reported. Initial diagnoses were made at ages ranging from 12 to 32, with epiphyseal fusion complete in all patients. During 6 to 10 years of corticosteroid therapy there occurred substantial reduction of hypertrichosis, disappearance of temporal recession, and decrease in eroticism. In 11 patients menstrual bleeding occurred within 4 months. Urinary excretion of total gonadotropins remained unchanged; total estrogens decreased slightly. By the end of followup, 7 patients with a mean age of 17 years had regular menses, 6 were ovulating, and I had a pregnancy. The other 5 patients, who continued to have irregular, anovulatory menstrual cycles, had a mean age of 28 years. The findings suggest that when excessive androgenization continues for a considerable period of time after puberty (as judged by bone age) noncyclic functioning of the gonadotropic mechanism is rendered irreversible.