SUMMARYTwo female volunteers, of menstrual age, with severe idiopathic hirsutism were treated for eight cycles and fifteen cycles respectively with cyproterone acetate 50 mg twice daily on days 5‐14 of the cycle. In all but one cycle, ethinyl oestradiol in a dose of 50 μg daily from day 5 to day 21 was given in addition. Cyproterone acetate when given alone abolished the mid‐cycle LH surge. Combined therapy with cyproterone acetate and ethinyl oestradiol produced a significant improvement in both patients’hirsutism and was accompanied by a marked reduction in the urinary excretion of LH, FSH and androgens and by a fall in plasma testosterone. However, the clinical benefit derived from this drug was due principally to its action as a peripheral antian