(Summary) A commercially-available A cold aerosol nozzle was used to disperse malathion, naled, and fenthion against caged female Aedes taeniorhynchus. Droplet size estimates of technical malathion ranged from 11-16 ยต mmd, depending on flow rate. Aerosols of malathion produced by the Leco ULV nozzle were consistently more effective than those produced by a high volume thermal nozzle. The estimated LD90s for malathion, naled, and fenthion were 0.025, 0.0095, and 0.0072lb/ac, respectively, based on the amount of active ingredient dispersed. There was no difference in the effectiveness of ULV cold aerosols dispersed at 10 and 20 mph.