This paper deals with the construction and use of a spinning disc atomizer that produces uniformly sized droplets. The device has a special use in the determination of the spread factor on several sampling surfaces (Kromekote paper, glass, plastic etc.). Furthermore, it permits the study of spraying performance, the inoculation of known spore doses of fungi and observations about toxical effects of pesticides on vegetables and animals. The apparatus showed a narrow droplet size spectrum, with a coefficient of variation about 2.36%. The spread factor of rodhamine B 0.2% in water solution showed to be of 1.32 and 1.71, respectively, when droplets of 98 and 325 micra were used, on Kromekote paper. With Malathion, 96% of active ingredient, the spread factors on Kromekote paper were 4.09 and 5.18 when droplets of 80 and 217 micra were spread. Melamine (Fórmica) showed a small variation in spread factor when sprayed with Malathion.