Technical Abstract: The control of arthropods that are vectors of human and animal disease is a high priority for both public health and military officials. As droplet size is a critical factor affecting vector control applications, the droplet size spectra produced by eleven sprayers and three spray formulations were evaluated. The droplet size spectra were measured by a laser diffraction instrument, a hot wire system (AIMS probe), and rotating slides. The information presented can be used by applicators to select the sprayer that produces the droplet size spectra needed for their particular application situation. There were considerable differences in the droplet size spectra produced by the different sprayers tested. The volume median diameter (VMD) for the water-based sprays ranged from 4.7 to 211 microns depending on the sprayer, and the percent of spray volume contained in droplets less than 20 microns ranged between 0.5-98.9 percent. The VMD for the oil-based sprays ranged from 9.4 to 125.3 microns and the percent of spray volume contained in droplets less than 20 microns ranged between 2.4 - 97.9 percent. The correlations between the VMD measured by the laser system and the mass median diameter, Sauter diameter, and VMD measured by the AIMS probe were all significant. Generally, the slide VMD’s were numerically similar to the VMD’s from the laser system and the Sauter diameter from the AIMS Probe.