Human exposure to preformed dialkylphosphates (DAPs) in food or the environment may affect the reliability of DAP urinary metabolites as biomarkers of organophosphate (OP) pesticide exposure. We conducted a study to investigate the presence of DAPs in indoor residential environments and their association with children’s urinary DAP levels. We collected dust samples from homes in farmworker and urban communities (40 homes total, n=79 samples) and up to two urine samples from resident children ages 3-6 years. We measured six DAPs in all samples and eight DAP-devolving OP pesticides in a subset of dust samples (n=54). DAPs were detected in dust with diethylphosphate (DEP) being the most frequently detected (>=60%); detection frequencies for other DAPs were <=50%. DEP dust concentrations did not significantly differ between communities, nor were concentrations significantly correlated with concentrations of chlorpyrifos and diazinon, the most frequently detected diethyl-OP pesticides (Spearman r=0.41 to 0.38, P>0.05). Detection of DEP, chlorpyrifos, or diazinon, was not associated with DEP and/or DEPþdiethylthiophosphate detection in urine (Kappa coefficients=-0.33 to 0.16). Finally, estimated nondietary ingestion intake from DEP in dust was found to be <=5% of the dose calculated from DEP levels in urine, suggesting that ingestion of dust is not a significant source of DAPs in urine if they are excreted unchanged.