Droplets of 95% malathion from a ULV aerosol generator were collected on silicone-coated slides, using the hand wave technique, by 3 researchers at 3 fixed distances. All combinations of 3 insecticide temperatures and 3 machine pressures were utilized for each distance. The droplet distribution of the aerosol was characterized by calculating 2 parameters: the volume median diameter (VMD) and the percentage of spray volume (PSV) in droplets less than 18u. Using normal operating procedures, it was found that sampling distance and machine operating pressure significantly affected the droplet distribution while neither the sampler nor the insecticide temperature were significant factors. There were no significant interactions between the 4 test variables indicating independence of each.