A LH-releasing hormone (LHRH) analogue was administered to subjects with elevated circulating LH concentrations and elevated androgens (polycystic ovary syndrome, PCO) and also to a control group with normal menstrual rhythm and normal LH and androgens. In both groups circulating LH concentrations were reduced to low and indistinguishable concentrations. Oestradiol, oestrone, androstenedione and testosterone levels were all reduced by treatment in both groups. However, the reduction in androgen concentrations was less marked in the patients with PCO. The oestrogen/androgen ratios remained relatively unaltered, but the testosterone levels remained slightly elevated in the PCO patients after treatment. The results suggest that patients with PCO syndrome show a disorder of androgen metabolism independent of elevated LH concentrations.