Between January 1980 and January 1990, a tumour of the testis in 12 of our patients was found to be a non-Hodgkin's malignant lymphoma (NHL). Age varied from 16 to 83 years, with 9 of them aged over 50. In 7 cases the pretherapeutic evaluation disclosed one or more other visceral sites of the tumour, and in 6 cases the tumoral diameter reached or exceeded 10 cm. Staging according to the Ann Arbor classification was: IE: 3 cases; IIE: 1 case and IV: 8 cases. The histological type assessed according to the international classification was: lymphoblastic (2 cases), small cell non cleaved of Burkitt's type (1 case), immunoblastic (2 cases), large cell diffuse (3 cases), mixed diffuse (3 cases), small lymphocyte diffuse (1 case) and unclassifiable (1 case). Seven patients underwent orchiectomy which, in 3 of them, was not followed by any other treatment. Nine patients were put on polychemotherapy which was intensive in 6 cases. Median survival was 30 months. Four patients, all treated intensively, are now in persistent complete first remission. This study confirms that NHL of the testis is rare and its malignancy in almost every case is either high or intermediate grade NHL. It occurs predominantly in elderly men. Advance prognostic factors are often present at diagnosis. However, the advent of intensive polychemotherapy seems to have transformed the course of the disease as well as that of other aggressive NHL's in more common sites.