This study was performed in two randomly defined groups of obese patients with polycystic ovaries to investigate the overall effects of hypocaloric diet combined (group 2) or not combined (group 1) with an antiandrogenic therapy (cyproterone acetate, 50 mg/day, plus ethinyl estradiol, 0.05 mg/day) on sex hormone plasma levels, insulin secretion and resistance, and body weight loss and on their reciprocal interrelationships. All obese patients with polycystic ovaries showed elevated luteinizing hormone and androgen levels, hyperinsulinemia, and marked insulin resistance. After an average period of 3 months both groups showed a similar weight loss and a similar reduction in the insulin-resistant state. During treatment in group 1 three patients had a greater frequency of menstrual bleeding, and in one of them an ovulatory cycle was documented. Whereas, no changes in gonadotropin and sex steroid levels were found in group 1, a significant fall was observed in group 2. No relationships were observed between these changes and those which occurred on insulin levels. We conclude that hyperandrogenism in obese patients with polycystic ovaries does not appear to be a primary factor leading to the insulin-resistant state.