The National Poisons Control Centre of the National Institute of Public Health and the Environment in the Netherlands conducted a prospective study on acute poisoning arising from exposure to pesticides in agricultural workers. The study was performed to determine the extent and severity of acute pesticide poisoning in the Netherlands and the working conditions that lead to these poisonings. All cases of potential acute occupational intoxication by pesticides in which the Poisons Control Centre was consulted in 1991 were thoroughly studied by an occupational hygienist and a specialist in internal medicine. With the consent of the patients and their physicians, the patients' medical condition and the working conditions leading to exposure were investigated on the spot. After the exclusion of 73 patients (27 non-occupational exposures, 7 occupational exposures in non-agricultural workers, 1 accident occurred abroad, 32 patients with illnesses unrelated to pesticides and 6 who could not be traced for follow-up), 54 cases of possible acute work-related pesticide poisoning remained for study. In 37 of the 54 events there was a direct relation between exposure to pesticides and acute health problems. In one patient doubt remained about the origin of the complaints and in 16 of the 54 cases pesticide poisoning was highly unlikely and the complaints could be attributed to other diseases. In the 37 remaining cases symptoms consisted of skin and/or eye lesions (23 cases) and systemic health effects (14 cases). Exposure to the soil disinfectant 1,3-dichloropropene resulted in severe skin damage. Direct contact of pesticides with the eyes invariability resulted in local irritation. Severe systemic poisonings occurred after exposure to organophosphate and carbamate insecticides and the soil disinfectant methyl bromide. Investigations at the site of the exposure revealed 43 cases of clear exposure to pesticides, in which, except for two cases, 1 worker per incident was involved. In 67% of the cases exposures took not place during pesticide dissemination, but during preparatory activities (35%), repair of application equipment (14%) and during re-entry (14%). In 79% of the cases splashing of pesticides or spray drift led to the exposure. In most accidents (74%) imperfect technical design or technical defects were important risk factors for exposure. Although most workers were aware of the risk of using pesticides, they were still careless in taking adequate protective measures. Especially during preparatory and reparations activities the wearing of protective clothing has to be emphasized.