Radiologic investigation of the male breast has given us a better knowledge of its physiopathology. We have reviewed more than 100 cases of breast tumors in male patients. We wish to describe the radiologic presentation of these lesions, the commonest of which is gynecomastia, to distinguish between cancer and gynecomastia, and to compare male breast cancer with female breast cancer. Examination of the breast in man is important. In the adolescent with an enlarged breast, examination may reveal a testicular tumor, whereas in the adult, where a malignant tumor of the breast must excluded, mammography is particularly helpful.