To elucidate the hypothetical role of a primary germ cell defect in the development of a germ cell tumor, with subsequent testicular dysfunction, the authors studied a series of men who had surgery performed for a benign sacrococcygeal teratoma when newborns. The mean levels of serum testosterone and gonadotropins did not differ from the control patients. However, gonadotropin-releasing hormone stimulation caused exaggerated responses of serum luteinizing hormone and follicle-stimulating hormone. Testicular size was small in three of eight patients. Semen analysis showed abnormal semen quality in five of eight patients. Only one patient had no evidence of testicular dysfunction. The results indicate that men born with benign sacrococcygeal teratoma may have Leydig cell dysfunction, abnormal spermatogenesis, or both. It was speculated that the associated abnormalities may have a common etiology: for instance, they might be due to a congenital germ cell defect.