Samples of drinking water collected in Warka-Grójec region of central Poland were tested for the presence of pesticides. Data obtained from analysis of water samples will be used for future epidemiological and environmental studies in the region. Samples were collected during spring and autumn of 2002-2003 from dug wells, deep wells and water mains in 81 randomly-selected rural households scattered throughout this region of extensive agriculture. The concentration of pesticides from four main chemical groups was determined by gas chromatography: organochlorines (lindane, DDT, methoxychlor), triazines (atrazine, simazine), organophosphates (acephate, diazinon, fenitrothion) and pyrethroids (alpha-cypermethrin, deltamethrin). Two-year monitoring of drinking water samples indicated the presence of DDT and methoxychlor contamination. Pyrethroids were generally not detected, with the exception of alpha-cypermethrin found in only a few samples. Triazines were also found in water samples collected in the course of the study with higher incidence during spring period. Organophosphates were by far the most common contaminants of drinking water in this region. Almost all samples were contaminated by signifi cant amounts of fenitrothion. The present study reveals an urgent need for systematic monitoring of drinking water quality in regions of intensive agriculture, since they are highly vulnerable to pesticide contamination. Consumption of pesticide-contaminated water may have a negative impact on the population living in this area, which also requires scientifi c assessmen.