The content of total testosterone (T), dehydrotestosterone (DHT), androstenedione (A), estradiol (E2), luteotropin (LH) and follicle-stimulating hormone (FSH) was studied in patients with ovarian and idiopathic hirsutism by a radioimmunoassay. The level of T-E-binding globulin (TEBG) was determined by 3H-DHT binding. Concentrations of free and TEBG-unbound T, DHT and E2 were calculated on the basis of the mass action law. The level of free and TEBG-unbound T and DHT was found to be the most reliable marker of the excessive production of androgens in hirsutism. The level of total T and DHT was raised in 50-60% of patients with hirsutism. Patients with hirsutism of ovarian genesis were characterized by considerable blood elevation of LH and FSH with still greater values in patients with menstrual disturbance, and by a rise of an A level. Difference found in hormonal indices can be used in differential diagnosis of ovarian and idiopathic hirsutism.