In order to study the mechanism of action of androgen on pubic and scalp hair, we established these and skin epithelial cells in culture. Because 5 alpha-reductase has been suspected of playing a role in hair growth, we tested the possibility that these cells differ in their pattern of androgen metabolism. Furthermore, we tested the hypothesis that androgen exerts its distinctive effects on these hairs by differentially regulating keratin or DNA synthesis. Anagen hairs of men and women were plucked from the pubis or scalp vertex and were studied using an epithelial cell culture technique. DHT formation from [3H]T cultured skin cells increased in the following order: epidermal less than scalp less than pubic less than fibroblasts = 0.8:2.8:8.1:71%/mg DNA/min, respectively. Androstanediols were minor [3H]DHT metabolites of all these skin cell types. The only feature that distinguished among the cultured epithelial cells was the ratio of apparent 5 alpha-reductase (5 alpha-R) to 17 beta-hydroxysteroid dehydrogenase (17 beta-HSD) activity: this was significantly greater (P less than 0.05) in cultured pubic hair cells than in scalp hair or epidermal cells. Cultured scalp and pubic hair cells resembled freshly plucked hair follicle cells in their keratin pattern. 46, 50, 56 and 58 kdalton bands constituted 99% of the total keratins. This keratin pattern and the polygonal cell shape were also similar to that of cultured epidermal cells. However, this keratin pattern was distinctly different from that of hair shafts which have 53 and 63 kdalton keratins. Dihydrotestosterone did not affect the keratin pattern, pattern of incorporation of [35S]cysteine or [35S]methionine, or rates of protein synthesis or cell proliferation in cultured hair cells. Although the higher apparent 5 alpha-R/17 beta-HSD ratio of cultured pubic than of scalp hairs is compatible with modulation of hair development by androgen, these studies militate against the possibility that androgens directly affect hair cell proliferation or protein synthesis in pubic or scalp hair.