Hormonal measurements in some women with hirsutism often reveal little or no elevation in androgen levels to explain the disorder. Thus, it has been postulated that increased sensitivity of the hair follicle to androgen may contribute to the development of hirsutism in such patients. We, therefore, sought androgen receptor abnormalities in skin fibroblasts cultured from 10 hirsute women (ages 17-43) and normal or mildly elevated plasma testosterone levels (28-82 ng/dl). Androgen receptor content (Ro) and binding affinity (Kd) in cultured pubic skin fibroblasts were measured using a dispersed, whole cell assay. Ten such cell lines from these women were compared with 19 pubic skin cell lines from 9 normal volunteers (6 males and 3 females) and from 10 other subjects (males with gynecomastia or hypospadias). There was no statistically significant difference in the mean androgen receptor content (11,600 +/- 2700 (SE) sites/cell fibroblasts vs 7900 +/- 700 sites/cell or binding affinity (2.0 +/- 0.3 (SE) X 10(-9) M vs 1.5 +/- 0.2 X 10(-9) M, respectively) between the patients' fibroblasts and those of the controls. We conclude that hirsutism cannot be explained by abnormalities in fibroblast androgen receptor number or affinity. These observations do not exclude the possibility that other mechanisms might lead to increased peripheral androgen sensitivity in such patients.