Lymphoma presenting in the testis was evaluated in 24 patients. The tumours were classified according to both the Rappaport and the Kiel classification. The Rappaport classification yielded only two tumour types--15 diffuse histiocytic and 9 diffuse mixed histiocytic-lymphocytic, with no pure lymphocytic lymphoma. No difference in survival time was found between these two tumour types. According to the Kiel classification there were four histological tumour types--immunoblastic (11 cases), centroblastic (2), centroblastic/centrocytic (6) and polymorphic immunocytic (5). In comparison with the other tumour types, the centroblastic/centrocytic lymphomas seemed to be advantageous as regards survival. It is concluded that systemic treatment with chemotherapy in accordance with current principles for malignant lymphoma is indicated following orchiectomy in localised testicular lymphoma as well as in disseminated disease. The value of post-operative radiotherapy to regional nodes is questionable.