One of EPA's priorities is to determine the extent of pesticides occurring in the nation's ground water. While many individual, localized ground-water monitoring studies have been conducted across the country, there has been no comprehensive compilation of these results. In response to this, the EPA's Office of Pesticide Programs has developed the Pesticides in Ground Water Data Base. The data base contains information derived from monitoring studies conducted by pesticide registrants, universities, and government agencies. The data base identifies the pesticides that have been looked for in ground water, the areas that have been monitored, and the pesticides that have been detected. The data base was developed in the first quarter of 1988, and at the same time, a public docket was established so interested parties could have access to the source information. Following the development of the data base, the EPA has been conducting a program to assess the validity of the information it contains. At this time, the authors believe they have gathered sufficient information to provide the public with an interim report on the national status of pesticide residues in ground water.