Our prior studies have revealed multigenic pharmacogenetic models that are significantly predictive of various drug response phenotypes (e.g., drug resistance, drug clearance, drug toxicity, disease response) in children with ALL. The large number of candidate loci and the relatively small number of patients illustrate the fact that larger sample sizes are required to definitively establish these polygenic models. The fact that there were significant race/genotype interactions, such that predictions differed in whites vs blacks, highlights the need for adequate numbers of patients within racial and ethnic groups to allow differential analysis of genotypic predictors after adjusting for confounding demographic factors in pharmacogenetic studies via stratified design and analyses.