Gynecomastia is a proliferation of the glandular component of the male breast. Causes include altered estrogen-androgen levels, aging, puberty, chronic disease, tumors and drugs. The physician must determine whether the condition has a physiologic or pathologic cause. Pubertal gynecomastia is generally physiologic and regresses without treatment. The likelihood of pathology is increased in patients over 26 years of age who present with new-onset gynecomastia. A thorough history, a complete physical examination and an appropriate clinical evaluation facilitate the prompt diagnosis and treatment of this condition.