OBJECTIVE To evaluate the treatment with cyproterone acetate and ethinyl oestradiol of diffuse androgen-dependent alopecia in women. METHODS Twenty women were treated for a period of 12 months in a reverse sequential regimen employing cyproterone acetate (CPA, 50 mg once daily from Day 5 to Day 15) and ethinyl oestradiol (EE2, 30 micrograms once daily from Day 5 to Day 24 of the menstrual cycle), and 20 were left untreated and acted as controls. Half of each group had serum ferritin concentrations above or below 40 micrograms/l. METHODS Forty Caucasian premenopausal women aged between 18 and 47 years, presenting with diffuse androgen-dependent alopecia, were enrolled into this study. METHODS Hair variables were assessed initially by the unit area trichogram and again in the same sites 12 months later. Biochemical investigations were performed before treatment and after 3, 6, and 12 months. RESULTS In the treated group, a significant (P less than 0.01) mean increase in total hair density (hair/cm2) and meaningful hair density (non-vellus hair/cm2) was found in patients in whom the serum ferritin was above, but not below 40 micrograms/l. However, in the control group a significant (P less than 0.05) mean decrease in total hair density and meaningful hair density was observed after 12 months. No correlation between serum ferritin levels and the degree of hair loss within this group could be established. CONCLUSIONS Patients treated with the anti-androgen cyproterone acetate and ethinyl oestradiol respond best when serum ferritin is above 40 micrograms/l.