In an attempt to establish the incidence and duration of pubertal gynecomastia and to correlate the condition with other changes of puberty, 2,369 examinations were made of 1,890 normal boys in a Boy Scout camp. After excluding all obese boys, the data from 1,855 examinations were analyzed. The over-all incidence of gynecomastia was 38.7% (28.9% in Negroes). The peak incidence of 64.6% occurred in the 14- to 14 1/2-year-old group. In 27.1% of the cases it persisted through 2 seasons, and in 7.7% for 3 seasons. We recommend that adolescent gynecomastia should not be treated either surgically or with hormones, but that the boy and his parents should be assured that this is a normal phenomenon of puberty which will disappear within 1 or 2 years.