The effect of pesticides on human, animal and environmental health has been cause of concern in the scientific community for a long time. Numerous studies have reported that pesticides are not harmless and that their use can lead to harmful biological effects in the medium and long term, in exposed human and animals, and their offspring. The importance of early detection of genetic damage is that it allows us to take the necessary measures to reduce or eliminate the exposure to the deleterious agent when damage is still reversible, and thus to prevent and to diminish the risk of developing tumors or other alterations. In this paper we reviewed the main concepts in the field, the usefulness of genotoxicity studies and we compiled studies performed during the last twenty years on genetic monitoring of people occupationally exposed to pesticides. We think that genotoxicity tests, including that include chromosomal aberrations, micronucleous, sister chromatid exchanges and comet assays, should be considered as essential tools in the imple- mentation of complete medical supervision for people exposed to potential environmental pollutants, particularly for those living in the same place as others who where others have already developed some type of malignancy. This action is particularly important at early stages to prevent the occurrence of tumors, especially from environmental origins.