Primary non-Hodgkin's lymphoma of the testis is rare. From 1976 to 1989 32 patients have been registered with the British National Lymphoma Investigation and two with the Institute of Urology. All 34 patients had disease of high grade histology (BNLI) although in four patients there were some areas with features similar to those described in lymphomas of Mucosal Associated Lymphoid Tissue (MALT). Twenty-three of 34 (67.5%) patients had early stage disease (I/II); 17/34 (50%) achieved complete remission from their initial treatment, and the relapse-free survival of these patients was 66% at 5 years. The disease-free survival for the 34 patients as a whole was 33% and their overall survival 39% at 5 years. The life expectancy for those presenting with advanced (stage III/IV) disease was very poor (median survival 9 months) with a low complete remission rate from chemotherapy. The salvage rate from recurrent disease (17%) was poor. Bilateral testicular involvement (18%) and a high rate of central nervous system disease (21%) occurred in the series, and two patients were HIV positive. Stage at presentation was the most important prognostic factor.