A major share of the grain farming (wheat and soybeans) in the State of Rio Grande do Sul is in the Passo Fundo area. For crop pest control, large amounts of agrochemicals (fungicides, insecticides, and herbicides) are used. To evaluate the genotoxicity of these products, the micronucleus test was performed in farm workers directly exposed to these chemicals. Heparinized blood samples were drawn by venipuncture from 30 exposed workers and 30 non-exposed controls. Micronuclei frequency was evaluated by counting 1,000 binucleated cells per individual in both groups. Smoking habits, age, and duration of exposure showed no effect on the frequency of micronuclei in both groups. However, statistical analysis showed significantly higher mean numbers of binucleated cells with micronuclei in exposed individuals (14.3/1,000 cells) as compared to controls (7.1/1,000 cells), allowing the authors to conclude that the micronucleus test is an efficient biological assay for monitoring population exposure to mixtures of agrochemicals.