Biomonitoring of effects in agricultural workers is necessary to assess the individual risk of handling pesticides. In this study, biochemical and haematological parameters were measured to evaluate the effects of exposure to these compounds in agricultural workers. The study was carried out in 110 workers and 97 control subjects. Several haematological and biochemical parameters were analysed. Assessment of haematological parameters revealed that the mean cell volume and haematocrit levels were significantly lower in workers than in controls (P=0.002 and 0.013, respectively), while mean corpuscular haemoglobin concentrations were higher in workers (P<0.001). There was also a significant inhibition of butyrylcholinesterase activity in workers compared with that in controls (P<0.001). Assessment of biochemical parameters further showed significantly higher activities of transferases, lactate dehydrogenase (P<0.001), alkaline phosphatase (ALP) (P=0.006) and creatine kinase (CK) (P<0.015), as well as higher levels of proteins (P<0.001), creatinine (P=0.001) and urea (P=0.001) in workers compared with controls, along with significantly higher uric acid levels (P=0.012). Furthermore, the number of years exposed to pesticides predicted higher activities of alanine aminotransferase, CK, ALP, as well as uric acid levels. Overall, chronic exposure to pesticides appeared to affect several biochemical parameters. These biomarkers seem to be indicative of adverse effects of pesticides in agricultural workers, confirming their use for routine monitoring of effects.