Objective:To investigate the level and clinical implications of serum CD105,vascular endothelial growth factor (VEGF) and its receptor Flt-1 in acute lymphoblast leukemia (ALL) children. Methods:Serum levels of CD105,VEGF and Flt-1 were detected in 31 newly diagnosed ALL children and 10 health controls with double antibodies sandwich enzymelinked immurosorbent assay. Results:The serum levels of VEGF and Flt-1 were not significantly different between the newly diagnosed ALL children and the health controls. While the serum level of CD105 was significantly higher in the ALL children than that in the health controls (P < 0.01),and the level was significantly higher in the high risk ALL children than in the low risk group (P < 0.05). The serum level of CD105 was independent of sex,age,white blood cell count when diagnosed,and immunophenotype with or without myeloid antigens,but it was related to extramedullary manifestations such as enlargement of live,spleen and lymph nodes,and early treatment response (P < 0.05). The serum level of CD105 was not significantly different between ALL children with chromosome abnormality and without abnormality. Conclusion:There was no significant difference in the serum levels of VEGF and Flt-1 between the ALL children and the health controls. The serum level of CD105 might be helpful in guiding therapy and evaluating prognosis.