To evaluate the expressions of proliferative antigen Ki-67 and apoptosis-antagonizing protein Bcl-2 as well as their clinical significance, immunohistochemistry staining with SAP was used to detect Ki-67 antigen and Bcl-2 protein in 18 cases of children with acute lymphoblastic leukemia (ALL) and 43 cases of adults with ALL. The results showed that the levels of Ki-67 and Bcl-2 expression in children with ALL were lower than that in adults, but only Bcl-2 expression had significant difference. Both in children and in adults, the levels of Ki-67 expression in T-ALL and My(+) ALL were higher than that in B-ALL and null-ALL. The highest complete remission rate (CR) was seen in the group with lower expression of both indexes (Ki-67 and Bcl-2). The lowest CR rate was seen in the group with higher expression of both indexes. It is concluded that the levels of Ki-67 and Bcl-2 expression in children and adults with ALL were closely related with the subtype of ALL and chemotherapeutic effects.