In a retrospective clinical study of 208 previously untreated persons with non-Hodgkin's lymphomas the disorders were classified and staged according to the histopathologic criteria of Rappaport, Winter and Hicks and the Ann Arbor clinical staging classification.Nodular types constituted 22% and diffuse types 78% of the lymphomas. The nodular lymphomas were slightly more common in females and were clustered in the age range 30 to 90 years. The diffuse lymphomas were slightly more common in males; the age distribution was bimodal, with one peak in the age range 10 to 19 years and the other in the age range 60 to 69 years, but when the age distribution of the general population in which the lymphomas occurred was taken into account, the incidence of these lymphomas was found to be significantly higher (P < 0.001) in persons more than 69 years of age than in those 40 to 69 years of age.SURVIVAL CORRELATED WITH HISTOPATHOLOGIC TYPE: persons with nodular (follicular) lymphomas and diffuse lymphocytic well differentiated lymphomas had a significantly greater survival (P < 0.05) than those with other diffuse lymphomas. No significant difference in survival was noticed between persons with nodal and extranodal lymphomas.While Rappaport and colleagues' criteria are still very useful, it is important to recognize the nodular lymphoma as a specific entity requiring generally different management from diffuse lymphomas. Appreciation of the different biologic behaviour of the various lymphomas is important to clinicians planning therapy.