OBJECTIVE Two hundred forty cases of childhood gynecomastia were studied retrospectively. There were 13 cases aged 3 to 10 years and 227 cases aged 11 to 15 years. Of the 240 cases of gynecomastia, 160 presented with bilateral breast enlargement, 50, left breast enlargement, and 30, right breast enlargement. The etiology of gynecomastia of the 240 patients included adolescent breast hyperplasia (n=219), drug ingestion (n=2), and secondary causes (n=5). Fourteen patients did not show identifiable causes and were diagnosed as idiopathic gynecomastia. The 8 patients with identifiable causes received specific treatment. After 1-3 months of treatment, the breasts of the patients improved. The 219 cases of adolescent breast hyperplasia and 14 cases of idiopathic gynecomastia were not given any medication. They were followed up regularly. Most of the patients recovered well within a 27-month follow-up.