The markers, CD11b, CD11c, CD14, CD21, CD23, CD25, CD38, and FMC7 were correlated with morphologic and other laboratory and clinical characteristics of 127 patients with untreated CD5+ chronic lymphocytic leukemia (CLL). Only CD38 and CD21 were significantly associated with atypical CLL morphology. The integrin associated markers CD11b and CD11c were associated with lower leukocyte count (white blood cell count [WBC]) and lower Rai stage. By contrast, the activation antigen CD23 was associated with a higher WBC, higher Rai stage, younger age group, and the presence of lymphadenopathy. Therefore, we conclude that CD23 positivity may reflect a more aggressive form of CLL, and CD11b and CD11c positivity a less aggressive form. The BCL-1 gene rearrangement was present in 5 of 84 (6%) CLL cases examined and was associated with atypical morphology and surface expression of CD11b. Patients with a BCL-1 gene rearrangement may represent a CLL subset or possibly a different B-cell disease.