Twelve boys, aged 12 to 19 years, with persistent gynecomastia were treated with the antiestrogen, clomiphene citrate, at a dose of 50 mg/day by mouth for one to three months. The mean breast size decreased by 0% to 36%, with only five boys experiencing a reduction of greater than 20%. Five boys subsequently required reduction mammoplasty. Levels of urinary gonadotropins, serum testosterone, and estradiol increased significantly during therapy. Since the ratio of testosterone to estradiol remained unchanged during treatment, the antiestrogen effects were achieved primarily at the level of breast tissue. Clomiphene citrate in a dose of 50 mg/day resulted in only small decreases in persistent pubertal gynecomastia and was not a satisfactory medical therapy for the condition.