In patients with adrenal hirsutism or enzyme deficiencies in steroidogenesis, elevated adrenal androgens could be normalized by dexamethasone. We were interested to see if dexamethasone would be as effective as cyproterone acetate in treating hirsutism in selected patients with adrenal pathogenesis. Therefore 28 patients with hirsutism of adrenal origin or enzyme deficiency were treated cyclically either with cyproterone acetate and ethinylestradiol (2 mg cyproterone acetate + 0.035 mg ethinyl-estradiol days 1-21, +10 mg cyproterone acetate days 1-15) (n = 15) or with 0.25-0.5 mg dexamethasone daily at 10 pm (n = 13). In the dexamethasone group there was a significant drop in dehydroepiandrosterone and dehydroepiandrosterone sulfate levels within 9 months, but there was a diminution in hirsutism in only four women (31%); in four out of seven menstrual irregularities decreased. In the cyproterone acetate group hirsutism diminished significantly in 66% (n = 10) without suppression of adrenal androgens. Weight gain occurred in a few cases in both groups; other side effects developed in 33% in the cyproterone acetate group. Preselection of patients with hirsutism is useful with respect to diagnosis; adrenal pathogenesis should not generally indicate dexamethasone treatment of hirsutism unless there is a desire for pregnancy, because cyproterone acetate is a more powerful agent in reducing hair growth.