Human scalp hair follicles of both sexes actively metabolized dehydroepiandrosterone-4-14C or dehydroepiandrosterone-15-3H in vitro. The principal metabolites were 7α-hydroxy-dehydroepiandrosterone, 7-keto-dehydroepiandrosterone, 5-androstene-3β,17β-diol, 4-androstene-3, 17-dione and 5α-androstane-3,17-dione. Testosterone or 5α-dihydrotestosterone were not detectable. Dehydroepiandrosterone-l,2-3H-sulphate was not converted to free dehydroepiandrosterone, but sulphoconjugation of the free steroid occurred to a limited extent. The metabolic activity of the follicular bulbs was several times higher than that of the sheaths. No sex differences were detected in the quality or quantity of the major metabolites isolated. Hair follicles obtained from balding men, however, exhibited severe metabolic deviations from the control pattern of metabolism seen in non-balding individuals.