Human biomonitoring provides an efficient and cost-effective way to identify and quantify exposure to chemical substances, including those having deleterious eff ects on human organisms. Once the risk of hazardous exposure has been identified and the mechanism of toxic eff ects has been elucidated, an ultimate decision about how to reduce exposure can be made. A particularly high risk of exposure to hazardous chemicals is associated with the use of pesticides in agriculture, especially the use of organophosphorous pesticides (OP), which are the most widely and commonly used insecticides worldwide. There is some strong evidence that chronic exposure to these compounds may have adverse eff ects on health. Exposure to pesticides has been associated with an increase in the incidence of non-Hodgkin's lymphoma, multiple myeloma, soft tissue sarcoma, lung sarcoma, and cancer of the pancreas, stomach, liver, bladder and gall bladder, Parkinson disease, Alzheimer disease, and reproductive outcomes. In view of these findings, the detection of populations at risk constitutes a very important topic. The biomonitoring studies on individuals exposed to pesticides have shown an elevated level of indicators of DNA damage, such as chromosomal aberrations (CA), sister chromatid exchanges (SCE), micronuclei (MN), and recently, single cell gel electrophoresis (SCGE). The cytogenetic markers of DNA damage have become very popular and useful in providing an analytical data for risk assessment, such as internal exposure doses and early biological eff ects of both occupational and environmental exposure to pesticides. The article describes the usefulness and the limitations of these biomarkers in biomonitoring studies of populations exposed to pesticides, with regard to the main routes of uptake and different matrices, which can be used to monitor risk assessment in occupational settings. The article also summarizes the latest reports about biomarkers of susceptibility, and mentions other biomarkers widely used in biomonitoring studies, such as pesticide or its metabolites level.