Pesticide exposure may be associated with increased risk of genotoxicity and carcinogenesis. These risks may be affected by polymorphisms of genes for glutathione transferase-dependent metabolism of pesticides and for DNA repair. We studied the prevalence of GSTP1 and XRCC1 polymorphisms and their possible correlation with DNA damage following prolonged pesticide exposure. DNA damage was estimated by the comet assay in peripheral blood samples from 51 pesticide-exposed workers and 50 controls. GSTP1 (105) and XRCC1 (399 and 194) genotypes were identified by restriction fragment length analysis. Individuals carrying theGSTP1 Ile-Ile or XRCC1399 Arg-Arg genotypes showed greater DNA damage than observed for other alleles.