Ovulation detection by following ovarian follicular growth via ultrasound scanning was investigated among healthy volunteers with regular ovarian function, among women taking oral contraceptives (OCs), and among infertile patients being treated with clomiphene. The study was longitudinal and began on Day 7 of the menstrual cycle. A Kretz Combison 100 sector scanner was used to visualize the ovaries every 1-3 days for morphological changes consistent with follicle development, ovulation, and corpus luteum development. These morphologic changes were correlated with daily urine hormone measurements. Based on luteinizing hormone peak, the estimated time of ovulation by scanning overlapped by 24 hours in 19 of 23 normal cylces and in 5 of 6 cycles treated with clomiphene. All 3 of the women did not ovulate while taking OCs, according to luteinizing hormone peak and ultrasound scanning. Follicular diameter was precluded as a single index for determining ovulatory changes, since there was found to be a wide range of preovulatory diameters; however, by measuring the maximal diameter of the follicle and observing morphological changes within the ovary from follicle to corpus luteum, ovulation could be detected in more than 80% of the cycles. 18 women were healthy volunteers; 3 women were taking OCs; and 5 women were being treated with clomiphene.