Signs and symptoms of excessive androgen secretion (hyperandrogenism) in adolescent and adult women include hirsutism, severe acne, and irregular menses. Because of the clinical features associated with hyperandrogenism, male adolescents do not usually present with signs or symptoms of androgen excess. This chapter focuses on causes of hyperandrogenism in adolescents, especially adolescent girls, including disorders of steroidogenesis, gonadal dysgenesis, Cushing's syndrome, tumors, and glucocorticoid resistance. Because polycystic ovary syndrome is discussed thoroughly in another chapter, it is not included. Brief discussions of androgen metabolism and steroidogenesis are followed by particulars of specific disorders. The chapter concludes with suggestions about differential diagnoses.