To investigate the biological features of leukemic cells in bcr/abl fusion transcript-positive B-lineage acute lymphoblastic leukemia (B-ALL), 3- or 4-color flow cytometry with directly conjugated monoclonal antibodies was used to detect the immunophenotype of the cells in 26 patients with bcr/able-positive B-ALL and 32 patients with bcr/abl-negative B-ALL. bcr/abl fusion transcript was detected by RT-PCR. Immunoglobulin heavy chain (IgH) gene rearrangement was detected by PCR. The results showed that all of the B-ALL patients were positive for CD19. There was significant difference in expression of CD34 (96.2% vs 65.6%), CD10 (96.2% vs 71.8%) and CD38 (43.8% vs 95.4%) between bcr/abl-positive and -negative groups. In bcr/abl-positive B-ALL group, the co-expression rates of CD10(+)/CD19(+)/CD34(+), CD10(+)/CD34(+)/HLA-DR(+) and CD10(+)/CD34(+)/CD38(-) were 92.3% (24/26), 73.1% (19/26) and 56.2% (9/16), respectively. In bcr/abl-negative group, co-expression of CD10(+)/CD19(+)/CD34(+) and CD10(+)/CD34(+)/HLA-DR(+) were 43.8% (14/32) and 37.5% (12/32), respectively, there were significant differences (P < 0.05) between bcr/abl-positive and -negative groups, but none of the cases co-expressed CD10(+)/CD34(+)/CD38(-). The detection rate of monoclonal IgH gene rearrangement (58.8%, 10/17) was lower in bcr/abl-positive group than that (85.7%, 12/14) in bcr/able-negative group. It is concluded that the expression rates of CD34 and CD10 are higher, and CD38 and IgH gene rearrangement are lower in bcr/abl-positive B-ALL cases, CD10(+)/CD34(+)/CD38(-) is a unique feature of immunophenotype, and this phenotype of leukemia cells is closer to that of early B-lineage progenitor cells.