Thirty-four HIV-positive men with gynecomastia were seen in an HIV outclinic during a 20-month period (incidence of 2.4 cases/100 patients receiving HAART per year). It developed mainly in subjects having good immunologic and virologic status, after an average of 3 years of HAART. No hormone abnormalities were found, or association with specific drugs. Although initially unilateral, more than half of cases progressed to bilateral gynecomastia. Spontaneous resolution occurred in most subjects with 12 months without modifying therapy.