We describe an adolescent Japanese girl with acanthosis nigricans and irregular anovulatory menstruation following menarche. Serum LH levels were elevated, whereas serum FSH levels were within normal range. An exaggerated response to LHRH was observed. Further, serum androstenedione levels were markedly elevated. Ultrasonogram revealed bilateral polycystic changes of ovaries. She had a mild degree of insulin resistance. Insulin binding studies using erythrocytes demonstrated a decreased binding capacity of insulin.From the above findings, this patient presents the syndrome consisting of hyperandrogenism, insulin resistance, and acanthosis nigricans and also has clinical and biochemical features compatible with polycystic ovary syndrome.