A retrospective analysis was performed upon 175 patients with Non-Hodgkin's Lymphoma involving the gastrointestinal tract and entered into BNLI trials and studies between 1974-1988. Malignant histiocytosis of the intestine (MHI), which was present in 16 patients, was associated with a survival of less than 25% at 18 months, and probably accounted for the poor survival of patients with jejunal involvement. Histopathological evidence of tumour origin from mucosa-associated lymphoid tissue (MALT) was found in 50% of patients with gastric involvement and in 27% of those with intestinal involvement. The overall survival of the series as a whole was 44% at 10 years. Multivariate analysis identified evidence of tumour origin from MALT as the only factor to attain prognostic significance in patients with gastric involvement, and clinical stage and the presence of MHI as the only factors to attain prognostic significance in patients with intestinal involvement. It is suggested that there is a need for a large multicentre prospective study of GIT lymphoma.