-Dispite significant improvement of leukemia treatment on past two decides, about one third of children treated for acute leukemia relapse. No individual predictive factor has yet been found to identify this subgroup of patients. Remarkable advances have been made in our understanding of molecular pathogenesis of acute leukemia with cytogeitics and molecular genetic data guiding successive improvement in treatment and risk prediction. Since most of relapses stem from cells of original leukemic clone, assment of minimal residual disease may help to evaluate the efficacy of therapy, predict impending relapse and alternatively permit individualization of therapeutic protocol. As the overall gall of therapy is eradication of leukemic clone and restoration of normal hematopoises, this is usually accomplished through use of myelosuppressive chemotherapy. During the last few year new adias was found for treatment such as gene therapy, monoclonal antibodies therapy, ATRA in promyelocytic leukemia and arsinic trioxide.