The correlations between increased expression of the MDR-1, MRP and LRP genes and the following variables of clinical and laboratory importance in childhood acute lymphoblastic leukemia were also calculated: age upon diagnosis, leukocyte count, race, immunophenotypic classification, FAB classification, presence of the CALLA marker, infiltration of the central nervous system, minimal residual disease on day 28 of induction, risk of relapse, and occurrence of relapse or death (Table 2). The gene discussed is ABCB1; the disease is acute lymphoblastic leukemia.