Our previous study has demonstrated that ovulation in unstimulated cycles is random with an equal likelihood of ipsilateral or contralateral ovulation occurring in the following cycle. This study evaluated women taking ovulation-inducing drugs to see if the side of ovulation in the preceding cycle has an influence on the side of ovulation in the succeeding cycle. Ovulatory patterns in consecutive pairs of cycles in anovulatory women treated with ovulation-inducing drugs were evaluated through sonographic studies of follicular maturation. The results demonstrated that when unilateral ovulation occurred, there was an equal likelihood of ipsilateral or contralateral ovulation in the succeeding cycle. However, ovulation-inducing drugs increase the incidence of bilateral or multiple ovulation.