This paper presents the results obtained within the framework of an EU research project aimed at investigating the relationship between occupational exposure to pesticides and the induction of cytogenetic damage. Populations from Greece, Spain, Poland and Hungary, all of them characterised by intensive agricultural activity, were the subject of the study. A total of 239 agricultural workers and 231 unexposed controls were examined for cytogenetic effects in lymphocytes of peripheral blood and exfoliated cells of the oral mucosa. The frequency of micronuclei (MN) was evaluated in both cell types and their relationship to different confounding factors (e.g. sex, country, smoking habit, etc.) was determined. The cytokinesis block proliferation index (CBPI) was also calculated to detect possible variations in the proliferative kinetics of lymphocytes due to pesticide exposure. The results obtained indicate that there are no increases in MN frequencies in the agricultural workers when compared with the controls for either lymphocytes or buccal cells. However, exposed individuals showed a significant decrease in CBPI when compared with controls. When the effect of the different confounding factors was evaluated, age was positively related with MN in lymphocytes and the Polish population showed a MN frequency significantly higher than those observed in the other populations. For buccal cells, the Spanish population showed a higher MN frequency, attaining significant differences in comparison with the other populations. Finally, the CBPI was found to be inversely influenced by age and Hungarian exposed men were the group that showed the lowest values.