The incidence of pubertal gynecomastia was determined in 646 Turkish boys in Ankara. A marked increase in the incidence was observed at Pubertal Stage 4 (60.2%) and age 14 years (61.1%). The incidence of gynecomastia during puberty at various pubertal stages and ages was 34.6%. Although the incidence of unilateral gynecomastia was 19.6%; there was no difference between right or left involvement.