A 39-year-old male was referred to our hospital in June, 1993, because of leukocytosis. Physical examinations showed massive splenomegaly without any lymphadenopathy. The white blood cell count was 13,800/microliters with 87% morphologically mature lymphocytes. Bone marrow aspirate revealed hypercellularity with 67% lymphocytes morphologically similar to peripheral lymphocytes. The lymphocytes displayed monoclonal rearrangements of immunoglobulin genes and the phenotype of CD5-CD19+CD20+ CD21+ and Smlg+. Splenectomy was effective against neutropenia and thromboytopenia. The clinical and laboratory findings of this case were unusual compared to those of typical B-CLL in massive splenomegaly, no lymphadenopathy and CD5-phenotype, suggesting the heterogeneity of B-CLL.