We are conducting a pilot study to test the hypothesis that environmental exposure to pesticides in pregnancy or during the neonatal period, together with genetic susceptibility may lead to childhood ALL or brain cancer. The study is a multicenter, case-control study, based on collaboration between clinical researchers and basic science research to evaluate the risk for childhood cancer in relation to measured levels of pesticides (and their metabolites) and genetic polymorphisms. Biomarkers will be used to examine the risks of chronic low-dose exposures, and to characterize relationships between specific pesticides, childhood cancer and genetic susceptibility.