PIP: The sample consisted of 33 patients who had had abortions in the 7-18 week of pregnancy, except 1 case where the duration of pregnancy had been 25 weeks. In 21 cases legal interruption of pregnancy had been carried out. The remaining 12 came to the hospital after the onset of bleeding. Methods used for the determination of ovulation were measurements of the basal temperature, cytological smear, and single endometrial biopsy. The interval between abortions and the onset of menstruation was 25-64 days, the average being 39 days. Endometrial biopsies were done on all patients 16-39 days after ovulation. The first cycle after abortion was determined to be anovular in 25, and probably so in 4 others, while ovulation had occurred in 4. In the 21 patients having had therapeutic abortions ovulation had occurred in only 1 while in the 12 patients who had had spontaneous abortions ovulation occurred in 3. Histological findings were hyperplastic endometrium in 3, endometritis in 6 and retained fragments in 5. Check-up examination of 27 patients at the second menstrual period established that 15 had ovular cycles. Patients having legal abortion were routinely given 5 mg of estradiolbenzoate a day to a total of 10-15 mg. It is thought that this dose of estrogen may depress pituitary activity and thus disturb the mechanism leading to normal ovulation. Of 41 cytological vaginal smears 15 could not be analyzed owing to infection. All but 1 of the remaining showed results consistent with those obtained by biopsy.