This work deals quantitatively with the generation, dispersion, and deposition of pesticide droplets on vegetation and with off-target drift of undeposited droplets. A computer simulation model for calculating dispersion, deposition, and drift is described, with comparisons between calculated results and field measurement results. The model includes the effects of aircraft vortex, atmospheric turbulence, droplet evaporation, and droplet deposition on foliage. Model output includes values of droplet deposit density and size on foliage and ground as well as droplet concentration and size in the drift cloud. In addition, a detailed description of droplet atomizer characterization methods is presented along with a large number of atomizer spectrum results for atomizers in current use. An analysis of a number of forestry spraying innovations is presented. This text should be a useful tool in assessing the efficacy and environmental impact of proposed and actual forest spray operations.