Gynecomastia is common in adolescents and adults, and reflects an underlying imbalance in hormonal physiology in which there is an increase in estrogen action relative to androgen action at the breast tissue level. Most patients have persistent pubertal gynecomastia or breast glandular enlargement from medications, age-related reduction in testicular function, or idiopathic causes. Gynecomastia must be differentiated from pseudogynecomastia due to increased breast adipose tissue, as well as from breast carcinoma. The evaluation of the causes of gynecomastia can be accomplished through history, physical examination and a few laboratory tests. Painful gynecomastia of recent onset may respond to antiestrogen therapy. Surgical removal is the mainstay for long-standing gynecomastia or glandular enlargement that is unresponsive to medical therapy.