Abstract
Periodic uterine bleeding occurs in spayed monkeys injd. dally with constant threshold amts. of estrone. In 2 monkeys such threshold cycles have occurred without interruption for as long as 3 yrs. Stilbestrol produces the same effect in doses 1/3-1/4 that of estrone. The exptl. intermenstrual period (40-42 days) is longer and more variable than the normal menstrual cycle.