Studies have demonstrated genotoxic effects by the presence of micronucleus in exfoliated cells from the buccal mucosa of agricultural workers exposed to pesticides. This study has assessed the genotoxic effects of pesticides on 61 agricultural workers from the state of Piauí, Brazil. 31 individuals were exposed to pesticides and 30 are from the same area, but were not involved in pesticides application. Cytogenetic damage were evaluated through micronucleus test in cells from the buccal mucosa and some parameters such as hematological and levels of enzymes. Exposed individuals exhibited cytogenetic damage with increased number of micronuclei in cells from the buccal mucosa in comparison with subjects from the control group with significant statistical difference (P < 0.01). We perceive that there is a statistically no significant (P > 0.05) increase in levels of plasmatic and eritrocytaireacetylcholinesterase and no statistically significant increase of phosphatase alkaline were detected in exposed workers in relation to the control group. No association was found in relation to smoking habits, alcohol consumption, protection utensils and the biomarkers analyzed or the biochemical analysis. Analysis of variance revealed a correlation between occupational exposure to pesticides of workers in Piauí and the presence of micronuclei (P < 0.05).