Objectives: Identification of parameters associated with measured pesticide exposure of farmers in open-field farming in France., Methods: Open-field volunteer farmers were monitored during 1 day use of the herbicide isoproturon on wheat and/or barley during the winters 2001 (n = 9) or 2002 (n = 38) under usual conditions of work. The whole-body method was used to assess potential dermal exposure using coveralls and cotton gloves. Mixing-loading and application tasks were assessed separately with 12 different body areas (hands, arms, forearms, legs, chest, back and thighs) measured for each task (mixing-loading and application separately)., Results: Daily potential dermal exposure to isoproturon ranged from 2.0 to 567.8 mg (median = 57.8 mg) in 47 farmers. Exposure during mixing-loading tasks accounted for 13.9-98.1% of the total exposure (median = 74.8%). For mixing-loading, hands and forearms were the most contaminated body areas accounting for an average of 64 and 14%, respectively. For application, hands were also the most contaminated part of the body, accounting for an average of 57%, and thighs, forearms and chest or back were in the same range as one another, 3-10%. No correlations were observed between potential dermal exposure and area sprayed, duration of spraying or size of the farm. However, a significant relationship was observed between exposure and the type of spraying equipment, with a rear-mounted sprayer leading to a higher exposure level than trailer sprayers. Technical problems, particularly the unplugging of nozzles, and the numbers mixing-loading or application tasks performed were also significantly related with higher levels of exposure., Conclusions: The main results obtained in this study on a large number of observation days are as follows: (i) the mixing-loading step was the most contaminated task in open field accounting for two-thirds of the total daily exposure, (ii) no positive correlation was noted with classically used pesticide-related parameters: farm area, area sprayed and duration of application and (iii) relevant parameters were the type of spraying equipment, the type and number of tasks and technical problems or cases of overflowing.