Abstract： Objective To detect the change of interleukin-18 (IL-18) level in the serum of patients with acute leukemia (AL) in children, and explore the clinical significance of IL-18. Methods The level of IL-18 was measured by sandwich enzyme-linked immuno-sorbent assay (ELISA) in 45 patients with AL in children. Results The leverof IL-18 in pre-treatment AL group was 719.35±358.21pg/mL and significantly higher than that of normal-control group [(311.80±146.64)pg/mL P <0.01]. Mter treatment, the level of IL-18 was 401.14±180.78 pg/mL in post-treatment complete remission group, which was significantly lower than that of pre-treatment group(P <0.01). The level of IL-18 in non-remission group was higher than those of normal control and CR group (P<0.01);while pre-treatment group the difference was not significant (P >0.05). According to the clinical sub-group with risk factors in pre-treatment AL, the level of IL-18 in high risk(HR) and middle risk(MR) group was significantly higher than low risk(LR) group (P<0.05). The level of IL-18 in T-ALL group was significantly higher than that in B-ALL group (P<0.05). The levels of IL-18 in pre-treatment AL were markedly correlated to the count of blast cells in bone marrow (r=0.411, P=0.005). Conclusion The level of IL-18 in the patients of childhood AL was in a high expression, and related to the clinical treating effect and the count of blast cells in bone marrow, which would be taken as an index of treating effect. The level of IL-18 was closely related to the clinical risk factors in pre-treatment AL.