Tumors of the epididymis, both primary and secondary, whether benign or malignant are very rare. The elements of the spermatic duct system, whether inside the testis or outside it in the epididymis and spermatic cord, exhibit only 1/20th of that of the germinal epithelium. In accordance with the mesodermal, or mesothelial origin of the whole spermatic ducr system, tumors of the epididymis and spermatic cord are - with few exceptions - mesenchymal tumors, the most frequent of these being the so-called adenomatoid tumor, a benign slowly growing tumor. With regard to the relative frequency of the various extratesticular tumors, a British panel has shown that one quarter of its cases are adenomatoid tumors, a second quarter sarcomas of children and juveniles (rhabdomyosarcomas and embryonic sarcomas), a third quarter sarcomas of adults and aged, while the last quarter includes simple benign mesenchymal tumors, mixed tumors, metastatic tumors, and others. There is only one extremely rare epithelial tumor of the epididymis, the papillary cystadenoma, which seems to be a partial menifestation or forme fuste of Hippel-Lindau's disease. So far only 40 cases have been described in the world literature. Therapy of intrascrotal but extratesticular tumors always ought to be surgical: if the tumor proves to be benign, simple excision suffices. In cases of malignancy, immediate inguinal lymphadenectomy and - as with testicular tumors - lymphography followed by retroperitoneal lymphadenectomy. Whether one should, in principle, then continue treatment either chemotherapeutically or radiotherapeutically, or do so only when there is evidence of metastasis, is a question whiich still remains open.