As part of a larger study to determine the prognostic significance of cell marker phenotype in diffuse lymphomas, 51 patients with monoclonal B-cell lymphoma were further characterized by receptors for C3 (EAC rosettes) as well as heavy and light chain phenotypes. Patients with greater than 10% EAC rosette-forming cells were found to have a statistically significant longer survival than those with less than 10% EAC rosettes (p = 0.005). A similar trend in survival duration was found for patients whose cells expressed mu heavy chain on their surfaces when compared to those with gamma heavy chain on their cell surfaces (p = 0.05). No difference was observed for light chain phenotype. No correlation was observed between these prognostic groups and any of the three most frequently used histologic classifications (i.e., Rappaport, Lukes, Kiel).