Examination of skin biopsy specimens from persons using anabolic-androgenic steroids demonstrates dramatic hypertrophy of the sebaceous glands. High dosages of testosterone and anabolic-androgenic steroids, often self-administered by athletes, increase skin surface lipids, the cutaneous population of Propionibacteria acnes and the cholesterol and free fatty acids of the skin surface lipids. Acne, oily hair and skin, sebaceous cysts, hirsutism, androgenic alopecia, striae atrophicae, seborrheic dermatitis, and secondary infections including furunculosis may occur in persons using these drugs.