Sixty-nine patients who had Ferriman/Gallwey hirsutism scores (FG) of greater than or equal to 8 were treated with Diane, an anovulant containing cyproterone acetate, 2 mg, an anti-androgenic progesterone and ethinyl oestradiol, 5.0 micrograms. Twenty-one of these had been previously treated with dexamethasone (DEX) and did not respond, i.e. FG greater than 50% of pre-treatment value. Prior to Diane treatment, plasma total testosterone (T) values, 1.4 +/- 0.5 nmol/l, mean +/- S.D., were similar to those in 43 normal women, 1.23 +/- 0.3 nmol/l, as were plasma androstenedione levels, 6.8 +/- 2.5 and 6.0 +/- 1.7 nmol/l respectively. However, plasma sex hormone-binding globulin (SHBG) values were suppressed being 36.2 +/- 16 nmol/l in hirsute women and 45.8 +/- 15 nmol/l in normal women, p less than 0.01. The T/SHBG ratio, an index of free testosterone, was elevated in hirsute women, 4.8 +/- 4.1, compared to values in normal women, 2.9 +/- 1.0, p less than 0.001. Following Diane therapy (2-24 months), 73% of patients responded clinically. There was no change in T, but SHBG was increased to 181 +/- 54 nmol/l, p less than 0.001 and T/SHBG was decreased markedly to 0.9 +/- 0.4, p less than 0.001. Androstenedione fell also to 4.8 +/- 1.7 nmol/l, p less than 0.001. The clinical and hormone response to Diane was similar in both DEX-resistant and previously untreated groups. We conclude that Diane is an effective agent in the treatment of hirsutism while it avoids the adverse effects of androgenic progesterone and of high dose cyproterone acetate therapy.