We conducted this study to establish initial base line data for the metabolism of 3H-steroid hormones (testosterone, dehydroepiandrosterone, progesterone, and estradiol) in skin and its appendages, the isolated sebaceous glands. Additionally, we wished to know whether or not changes occurring in aging skin and a relative lack of endogenous hormones alter the skin's capacity to metabolize steroid hormones in vitro. Eighty-seven biopsy samples from the preauricular area of the cheeks were obtained from 13 young women (ages 18 to 30) and 3 postmenopausal women (ages 60 to 68). Values were obtained for the rate of metabolism of tritiated testosterone, estradiol, progesterone, and dehydroepiandrosterone in the isolated sebaceous glands and dermis of the women. Wide individual variation was observed in sebaceous gland metabolism in both young and old women. The patterns of 3H-steroid metabolites contained in the dermis were similar in the younger and older women. However, the ratios of precursors to metabolites in the sebaceous glands of the older women differed from the ratios of the younger ones. The pattern of in vitro lipid synthesis from 14C-acetate in sebaceous glands of the 2 groups was not significantly different. The most interesting relationships derived from this study were the relative molar uptakes of 3H-steroids. Tritiated progesterone was present in much greater quantities than either 3H-androgens or 3H-estrogens, in both dermis and sebaceous glands. On a weight basis the sebaceous glands were much more active than the dermis in the metabolism of 3H-steroid hormones. Initial data of this type may be used as a conceptual framework within which changes associated with various pathologic and physiological states such as aging, acne, hirsutism, and alopecia can be examined.