To investigate the characteristics of immunophenotype of B-lineage acute lymphoblastic leukemia (B-ALL) cells in Chinese cases, B-ALL cells from 181 patients were analyzed by 4-color flow cytometry with CD45/SSC gating. The results demonstrated that the antigen expression frequencies were as follows: CD19 (100%), HLA-DR (98.9%), CD38 (88.5%), CD10 (76.8%) and CD34 (76.8%). CD117 and T antigens (CD2 and CD7) were rarely expressed. Childhood group (<or= 14 years) had the highest frequency of CD10. Adolescent (15 - 18 years) and adult groups (>or= 19 years) had a higher expression rate of myeloid antigens (CD13 and/or CD33). Subtype CD10(+)/CD34(+) took the highest percentage in three age groups. Percentages of CD10(-)/CD34(+) group increased by age. Subtype CD10(-)/CD34(+) had the highest myeloid antigen co-expression. Comparing with CD45-positive cases, those with CD45-negative or CD45(+/-) always had higher CD10 expression. Bcr/abl mRNA was evaluated in 43 samples from patients with B-ALL. Myeloid antigen co-expression was not different in bcr/abl(+) and bcr/abl(-) groups, and m-bcr/abl(+) was mainly observed in subtype CD10(+)/CD34(+). In conclusion, typical B-ALL cells expressed CD19(+), HLA-DR(+), and CD117(-). CD34, CD10 and CD45 expression varied in different maturation stages. The immunophenotypic subtype of B-ALL in adolescents was similar to that in the adults. Blasts with CD45(+) were mostly seen in CD10(-) cases. CD13 and/or CD33 co-expression was fewer in children patients. m-bcr/abl(+) was mainly seen in subtype CD10(+)/CD34(+).