Serial assays of testosterone, epitestosterone, oestrogens and pregnanediol in urine have been conducted in 11 hirsute patients and the results compared with those in 14 normally menstruating women. Overall mean levels for testosterone and epitestosterone were significantly higher in the hirsute group suggesting that excessive androgen production is of importance in the pathogenesis of this condition; significant differences in mean oestrogen and pregnanediol output between the two groups were not noted. In the hirsute subjects significant differences in urinary steroid excretion were not found between patients suffering from simple hirsutism and those in whom the excessive hair growth was associated with other pathological conditions. In both normal and hirsute groups steroid levels differed significantly between subjects and in individual women at different times. The incidence of anovulatory cycles was considerably higher in the hirsute than in the normal group.