Adult mosquito control practices generally employ chemical toxicants, and thus, unavoidably expose inhabitants of treated areas to insecticides. Human exposure to most organophosphate insecticides results in the excretion of specific urinary metabolites. In Dover, Delaware, urine specimens were collected from people residing in and adjacent to an area treated with naled for adult mosquito control. Chemical analysis of the spray solution revealed that it was contaminated with traces of temephos, another organophosphorous insecticide used in mosquito control. Urine samples from the same individuals were taken prior to and just after aerial spraying and analyzed for organophosphate insecticide metabolites. Levels of these metabolites varied; increases in dimethyl phosphate (from exposure to both temephos and naled) and dimethyl phosphorothionate (solely from Temephos exposure) in post-treatment samples could be attributed to this spraying. Metabolite levels observed in this study did not approach concentrations normally associated with cholinesterase inhibition or other clinical repercussions. Other aspects of human exposure to insecticides are discussed.