A sensitive and reliable method to assess occupational exposure to vinclozolin based on biomonitoring principles has been elaborated. The conditions for pretreating the human urinary samples were chosen in such a way that vinclozolin metabolites containing the intact 3,5-dichloroaniline (3,5-DCA) moiety are completely degraded into this amine by means of basic hydrolysis. After addition of 3,4-DCA as an internal standard, steam distillation and extraction, the analysis is carried out by high-performance liquid chromatography and electrochemical detection. The determination limit is 5 microg 3,5-DCA/l urine. The method turned out to be sensitive enough to quantify not only occupational but also nutritional excretions of 3,5-DCA containing metabolites to some extent. Interpreting these results, which are verified by an independent method, it must be considered that in addition to vinclozolin some further crop protection agents are also based on the 3,5-DCA moiety.