Three cases of combined pregnancy are described after gonadotropin therapy; two cases after human pituitary gonadotropin and one after human menopausal gonadotropin administration. In each case the intrauterine gestation was a multiple pregnancy. After salpingectomy, two of the women have proceeded to the delivery of healthy infants; the third woman aborted. In each case the gonadotropin stimulation regimen was ceased at the appropriate stage when the estriol excretion was between 60 and 125 micrograms/day, but the subsequent rate of rise of estriol was 2.3- to 3.2-fold during the coasting phase before the human chorionic gonadotropin trigger when the estriol excretion rate was 140 to 350 micrograms/day.