Gynecomastia is common, being present in 30% to 50% of healthy men. A general medical history and careful physical examination with particular attention to features suggestive of breast cancer often suffice for evaluation in patients without symptoms or those with incidentally discovered breast enlargement. Men with recent-onset gynecomastia or mastodynia need a more detailed evaluation, including selected laboratory tests to search for an underlying cause. Treatment depends on the cause and may include observation, withdrawal of an offending drug, therapy of an underlying disease, giving androgen or antiestrogen drugs, or plastic surgery.