Captive squirrel monkeys show a seasonal response to a subtle ovulation induction regime of five days of progesterone, four days FSH (1 mg/day) and a dose of HCG (500IU), with the minimal response occurring from July to September. A 3 x 3 factorial design with 18 adult female monkeys was used to determine the effects of increasing doses of HCG (500, 1,000, or 1,500 IU) and increasing dose or duration of FSH (1 mg for four days, 2 mg for four days, or 1 mg for five days) on ovulation between early July and mid-October. An increase in either dose or duration of FSH increased ovulation while increasing HCG was ineffective.