Since ALL is considered a multifactorial disease where xenobiotics could be important factors that contribute to its pathogenesis, and that NQO1, CYP2E1, and NAT2 are enzymes involved in the metabolism of xenobiotics (including benzene, cigarette smoking, chemotherapy agents, and alcohol drinking), which increase the risk to develop diverse human diseases (2, 11, 19), we used a MDR approach to identify combinations between genetic and environmental factors associated with ALL (29). This evidence concerns the gene NAT2 and acute lymphoblastic leukemia.