A diagnosis of chronic lymphocytic leukemia (CLL) was made in 81 patients referred for peripheral blood lymphocyte typing (PBL). A retrospective review was undertaken to see if correlations existed between surface marker phenotype-determined subclasses and clinical features. Surface markers utilized were surface immunoglobulin (sIg), sheep erythrocyte receptor (E), 65,000-dalton human T lymphocyte antigen (T65), Ia antigen, and for sIg+ cells, heavy and light chains. All patients were Ia+. Cells of 70% of patients were sIg+ E- T65+ Ia+, and the clinical heterogeneity was that of classical CLL. Eight of the nine patients with sIg+ E- T65- Ia+ cells had a paraprotein. The sIg- E+ T65+ Ia+ phenotype represented classical T cell CLL. Three of the five patients in the sEg- E- T65+ Ia+ group had significant albuminuria, and two had nephrotic-range proteinuria. Use of additional monoclonal antibodies to B cell surface antigens should further subclassify CLL and other lymphoproliferative disorders. Interesting clinical correlations with certain phenotypic subclasses do exist, and further subclassification and long-term follow-up may yield correlations between phenotypes and prognosis.