An 8-month-old boy who had a Sertoli cell tumor of the testis was alive and well 4½ years later. Review of the 23 patients with Sertoli cell tumor, including ours, showed 16 patients who were under 1 year of age. Two patients had a bilateral tumor. In another patient, it was located in an undescended testis. Sexual precocity occurred in one boy, and gynecomastia occurred in three boys, but regressed in two of them, following orchiectomy. Malignancy, as evidenced by retroperitoneal lymph node metastases, was present in only one boy. Since there are no clear-cut, gross or microscopical, pathological criteria to determine malignancy in this type of testicular tumor, careful follow-up is suggested.