Crop activities lead to dermal exposure of workers to pesticides. The efficacy of hand washing as a control measure is unknown. The efficacy of water and soap was studied for some pesticides and exposure situations. Pre-washing contamination levels in field studies were calculated from foliar residues by models using transfer factors. Between 24.5% and 50.7% of the calculated prewashing contamination was removed in two field studies with three pesticides, with coefficients of variation between 43% and 72%. In a human volunteer study, on average 45.8% and 85.7% was removed for two pesticides (coefficients of variation 6% and 7%). No influence of ‘washing vigour’ was found and efficacy did not depend on pre-washing contamination levels. The combination of field studies and laboratory experiments was successful, partly compensating for weaknesses in both approaches.