In a double-blind cross-over study, 24 hyperandrogenic women were treated for three months at a time with either spironolactone 100 mg or placebo daily from the 5th to the 21st days of the menstrual cycle. Spironolactone had a slight but statistically insignificant effect on hirsutism when compared with placebo. Slightly more regular menstruation and better follicular growth was noted during spironolactone treatment. Ovulation (defined as a day 21 serum progesterone level of more than 10 nmol/l) occurred in only 12% of spironolactone cycles, as against 28% of placebo cycles. Spotting occurred in one-third of the spironolactone cycles. No significant differences were found between spironolactone and placebo cycles in serum levels of LH, FSH, prolactin, estradiol, progesterone, androstenedione, total testosterone, sex-hormone binding globulin (SHBG), unbound testosterone, dehydroepiandrosterone sulphate (DHEAS), cortisol, potassium and sodium. The average ovarian volume was 13.0 (5.7-21.8) cm3, and no significant differences were found between treatment and placebo cycles. No significant effect of spironolactone could be demonstrated on androgen secretion and the incidence of ovulation.