This paper briefly reviews the various classifications proposed as alternatives to that of Rappaport. Rappaport's classification is valuable because it is applicable to clinicopathologic studies, but there are areas of contention. Following the Airlie Conference, which failed to resolve the current controversy about classification, the National Cancer Institute proposed to support a retrospective study of 1000 cases of non-Hodgkin's lymphoma, during which the various classifications will be applied to the biopsy slides by a selected panel of pathologists. It is hoped that this study will meet the urgent need for a classification which will eliminate controversial terminology and will employ terms acceptable to pathologists in their daily diagnostic work and to hematologists and oncologists burdened with the choice of therapy for patients affected by the non-Hodgkin's lymphomas.