Abstract: A droplet impact sampler based upon the stain technique for measuring airborne droplets comprises a magnesium oxide coated, graphite target located within a cylindrical sampler head below a pneumatically operated shutter. The shutter is opened for a predetermined time period to expose the target to the specimen droplets which stain the target upon contact. Droplet size is determined by measuring the stain diameters and compensating for a flattening effect of the droplet that occurs upon impact as a function of several parameters, such as contact angle, water density and surface tension. Rate of deposition is determined by correlating the number of stains counted on the target with the operating speed of the shutter.