Thirty-two women with polycystic ovary syndrome (PCOS) were allocated to two antiandrogen treatment regimens; 28 women completed the trial. Twenty women were treated with ethinyloestradiol and cyproterone acetate (EO-CA) cyclically for 6 months and eight women were treated with the gonadotrophin releasing hormone (GnRH) analogue, goserelin for 6 months. Effects on hirsutism, insulin sensitivity (estimated by glucose clamp technique), blood lipids and hormones were measured. Women treated with EO-CA showed a reduction in hirsutism (P <0.05), and decreased serum androgen concentrations (P <0.001) as well as reduced insulin sensitivity (P <0.05). In women treated with goserelin, serum androgen concentrations also decreased (P <0.001), but there was no significant reduction of hirsutism. This group, however, showed an improved insulin sensitivity (P <0.05) despite an unchanged body mass index. Bone mineral density was unaltered in both treatment groups. The reduction in androgen concentrations caused by EO-CA was not paralleled by increased insulin sensitivity, most probably due to the effect of ethinyloestradiol per se. In contrast, the reduction in androgen concentrations by goserelin was accompanied by an improved insulin sensitivity.