In October 2004, the Florida Department of Health (FLDOH) and the Centers for Disease Control and Prevention (CDC) assessed human exposure to ultra-low volume (ULV) aerial application of naled. Teams administered activity questionnaires regarding pesticide exposure and obtained baseline urine samples to quantify prespray naled metabolite levels. Following the spray event, participants were asked to collect postspray urine specimens within 12 h of the spray event and at 8-h intervals for up to 40 h. Upon completion, a postspray activity questionnaire was administered to study participants. Two hundred five (87%) participants completed the study. The urine analysis showed that although 67% of prespray urine samples had detectable levels of a naled metabolite, the majority of postspray samples were below the limit of detection (<LOD). Only at the “postspray 6” time period, which corresponds to a time greater than 5 half-lives (>40 h) following exposure, the number of samples with detectable levels exceeded 50%. There was a significant decrease in naled metabolites from prespray to postspray ( = .02), perhaps associated with a significant reduction (≤0.05) in some participants that may have resulted in pesticide exposure by means other than the mosquito control operations. These data suggest that aerial spraying of naled does not result in increased levels of naled in humans, provided the naled is used according to label instructions.