A statewide sampling program was undertaken to define the extent of agricultural chemicals in rural, private drinking water wells in Illinois. A stratified random approach was taken for selecting wells for sampling. Depth to the top of the uppermost aquifer material was taken as the stratification variable. A sample size of 384 wells from each of four identified strata was selected, and the number of wells in each stratum was based upon 95 percent confidence, 50 percent probability of occurrence, and a ±0.05 precision. Key components of the statewide survey include methods for well selection, inventory of land use around the wellhead, sample collection, quality assurance and quality control (QA/QC), sample chemical analysis, and information management. A pilot study has recently been completed to field test the design of the statewide survey, refine analytical methods for the chemical analyses, and to develop a computerized database for information management. The field and laboratory work are complete at this time.