Lymphoplasmacytoid (lpc) and small cell centrocytic (scc) lymphoma are the two major sub-types of diffuse low grade non-Hodgkin's Lymphoma (NHL) within the Kiel classification. The presentation features and outcome for all 112 patients with these diagnoses (60 lpc, 52 scc) managed at St Bartholomew's Hospital between 1972 and 1986 are presented. The outcome for these patients is compared with that for patients with follicular and high grade lymphomas managed at this hospital during the same period. Nineteen of the 112 patients had localized (stages I-IIE) disease. In 18 of these cases the primary site of disease was extranodal, the gastrointestinal tract being involved in 12 cases. The survival for patients with localized disease was excellent. Eighteen are currently alive with median follow-up of 8 years. Ninety-three patients had advanced disease. A high incidence of splenomegaly, hepatomegaly, bone marrow and peripheral blood involvement was observed in both histological subgroups. A monoclonal paraprotein band was detected in the serum of nearly 50 per cent of patients with advanced lpc lymphoma. Patients with advanced disease were treated with either chlorambucil or cyclophosphamide, vincristine and prednisolone (CVP). The outcome was similar for both histological groups. Survival for these patients was poor (median 40 months) with less than 20 per cent surviving 5 years. Advanced age, elevated aspartate transaminase and failure to respond to treatment were identified by multivariate regression analysis as adverse prognostic factors.