Concentrations of insecticides sprayed from truck or helicopter onto selected surface-water bodies in Suffolk County, N.Y., during the summers of 2002-04 decreased to below detection limits within 4 days after application. The U.S. Geological Survey (USGS), in cooperation with Suffolk County Department of Health Services (SCDHS), sampled surface waters from selected wetlands for insecticides that were sprayed seasonally from a truck or helicopter as part of the county’s West Nile Virus vector-control program. A total of 72 samples were collected from 27 sites and analyzed for 6 compunds—malathion, methoprene, methoprene acid, piperonyl butoxide (PBO), resmethrin, and sumithrin—that are typically used to help control mosquitoes. PBO was the most frequently detected analyte (33.3%), followed by resmethrin (11.1%), methoprene (9.7%), and methoprene acid (2.4%). Sumithrin and malathion were not applied and were not detected in any of the samples. Maximum recorded concentration of compounds in surface water were: PBO (59,800 ng/L), methoprene (9,030 ng/L), methoprene acid (1,710 ng/L), and resmethrin (293 ng/L). PBO and resmethrin were detected more often in samples when the compounds were applied by a helicopter rather than a truck. This report describes the 27 sampled locations, the sampling methods, and presents the initial results of the study. Detail is provided about concentrations of the applied compounds with respect to time as well as comparisons between the two application processes (truck versus helicopter). All data collected are presented in a table.