What are the long-term effects of hysterectomy on the ovaries of normal women? Ninety-three women aged 29–44 years (median, 38 years) who had undergone hysterectomy for benign reasons 0·3–9·1 years prior to investigation, contributed urine samples twice weekly for a period of 53–149 days (median 102 days) for pregnanediol analysis. The interval between successive pregnanediol peaks and their increment over baseline were measured. The median peak interval was 27·3 days, and 93·3% of all intervals were of 21- to 35-days duration. Of the 337 peaks observed, 96·7% met the criteria previously used to define an ovulatory cycle. These are similar to the figures reported for menstruant women of comparable age. ANOVA showed no significant effect of age or time since hysterectomy on either the interval between peaks or peak increment (P > 0·10 in all cases). The evidence suggests that the ovaries of women who have no uterus behave like those of intact women. Journal of Endocrinology (1992) 135, 597–602