Abstract: A method of providing contraception for and regulation of the menstrual cycle of a gonadal female mammal by a) administering thereto about once a week throughout her menstrual cycle an amount of a GnRH-antagonist effective to block folliculogenesis and thereby achieve a contraceptive state but less than the amount thereof required to block hormonogenesis; and b) inducing menses by administering during the last half of that cycle an amount of a progestin effective to produce a secretory endometrium and then terminating the progestin administration.