The sites and hormonal control of lipogenesis in hamster ear sebaceous glands are reported. Sebaceous lipogenesis was determined in ear biopsies by incubation with glucose and tracer concentrations of 14C-acetate in buffer. The 14C-labeled lipids were saponified, extracted, and determined by liquid scintillation counting. Histologically, the ears contained many sebaceous glands. The glands of male animals were much larger and more heavily lipid-stained than glands from females. Lipogenesis was almost entirely confined to the sebaceous glands in the dermal stroma. Lipogenesis was considerably higher in ear biopsies from male hamsters than from female, castrate male, or hypophysectomized male hamsters. In contrast to published data using hypophysectomized rats, where dihydrotestosterone potently and testosterone only weakly increased sebum secretion, both testosterone and dihydrotestosterone potently increased lipogenesis in the ears of hypophysectomized male hamsters. Dihydrotestosterone was somewhat more potent than testosterone in the hamster. Hypophyseal hormones do not appear to be essential for androgen stimulated lipogenesis in the hamster. In female hamsters, 5 alpha-androstane-3 alpha, 17 beta-diol, testosterone, dihydrotestosterone, 4-androstene-3,17-dione, and 5 alpha-androstane-3,17-dione produced dose-dependent increases in lipogenesis. From this and other studies, it is suggested that androgens other than dihydrotestosterone could be physiologically important in man and animals in stimulating lipogenesis in sebaceous glands.