Groundwater in the province of "Noord-Brabant" was investigated at some selected places for residues of pesticides. Aim of this investigation was to get more information about the threat of groundwater quality as a consequence of application of pesticides, in order to take possible measures for protection of groundwater quality in the future Groundwater below agricultural land where potatoes are grown contained residues of 1,3-dichloropropane in concentrations exceeding the EC- guideline of 0.1 mug/l for drinking water. All three samples contained this compound in a concentration range of 1.0 to 3.0 mug/l. As a consequence of application of herbicides in maize cultured land residues of atrazine and bentazon were found. Atrazine was found twice (0.13 and 0.19 mug/l) and a decompositionproduct, desethyl-atrazine was found four times (0.02-0.16 mug/l) while bentazon was found three times (0.02-0.07 mug/l).