The U.S. Environmental Protection Agency conducted a national survey to learn about the prevalence of 126 pesticides and pesticide degradates plus nitrates in public and private drinking water wells. This paper describes the statistical design and chemical methods used in the survey. Then, estimates of contamination rates for public and domestic water supply wells are presented. Progress regarding the investigation of the relationship among contamination patterns, pesticide use, and ground water vulnerability are reported. Finally, possible uses of the survey results in the Federal drinking water and pesticides programs are discussed.