To prove the significance of 4-color fluorescence labeling flow cytometric analysis for leukemia immunophenotyping, bone marrow and peripheral blood samples from 88 cases with acute leukemia were analyzed by means of flow cytometry with 4-color fluorescence labeling monoclonal antibodies (McAbs). More than 90% of cases could be classified into acute myeloid, T- or B-lymphocytic leukemia by staining with 13 different kinds of monoclonal antibodies within 4 tubes of combination of antibodies. AML-M(2) - M(7) could also be identified simultaneously. Another one tube of combination of 4 McAbs could be used for further subtyping of those who were undetermined by the above 4 tubes. Patients with AML-M(0)/M(1) which may be negative of myeloperoxidase (MPO) in cytochemistry can be identified by labeling with both membrane and cytoplasmic antibodies. In conclusion, the accuracy of leukemia immunophenotyping has been improved by 4-color flow cytometry analysis.