Two patients with acute lymphocytic leukemia of B-cell phenotype (B-ALL) are described. They were 77-year-old female and 34-year-old male. One patient presented with marked splenomegaly, and the other with rupture of spleen on admission. Leukemic morphology revealed a typical L3 profile by FAB classification system in both cases. Immunologic analysis showed the presence of surface immunoglobulins in both cases, and one phenotype was IgM kappa, whereas the other was IgG kappa. Cytogenetic study revealed the typical translocations (8; 14) in both cases. Following chemotherapy, complete remission was achieved in one case, but the other died 36 days after admission. Including our two cases, we studied 12 cases of B-ALL and 77 cases of Burkitt's lymphoma reported in Japan, investigating the clinical prognosis as well as the biological features. We concluded that there are no significant difference of survival between B-ALL and Burkitt's lymphoma. We estimated it is due to oncogenesis from the same original cell in despite of the difference in main tumor site between two diseases.