Ethynodiol (17alpha-ethinyl-4- estrene-3,17-diol) diacetate, a potent progestin and oral inhibitor of ovulation in the rabbit, gives evidence of possessing antiovulatory activity when it is administered orally to women. When it is combined with an estrogen it provides adequate control of menstrual cyclicity, and, thus far, complete contraceptive effectiveness even in low daily doses.