The breast is an important organ system for the adolescent female and occasionally for the adolescent male as well. This chapter reviews basic principles of breast concerns and disorders including congenital anomalies, asymmetric breast development, underdeveloped breasts, virginal hypertrophy, breast masses, mastaglia, galactorrhea, gynecomastia in males, and others. Clinicians should be attuned to issues and concerns for this important structure in adolescents