Field trials with ULV aerosols indicated that 2 formulations of permethrin (3-phenoxyphenyl) methyl Cis, trans - (+) - 3- (2,2-dichloroethyl) - 2,2-dimethylcyclopropane carboxylate), ICI-PP 557 and FMC-33297, and a new formulation of propoxur (o-isopropoxyphenyl methylcarbamate, Baygon ULV) were highly effective against caged adult females of Aedes taeniorhynchus (Wiedemann) and Anopheles quadrimaculatus Say. Droplet sizes of ICI-PP 557 and Baygon ULV were determined: volume median diameters of 8 and 9 pm were obtained for flow rates of 58 and 272 ml per min of ICI-PP557 and Baygon ULV, respectively. Additional tests with these same flow rates showed that these formulations would not cause damage to acrylic lacquer automotive paints, even with gross over exposure. All aerosol applications were made with a Leco HD aerosol generator operated at 4 psi/nozzle air pressure.