The database contains ground-water nitrate and pesticide data that have been compiled from federal, state and local agencies and the University of Nebraska; screened for essential data elements; evaluated using established criteria; and assigned a quality flag that corresponds to one of five quality assessment levels. Each quality assessment level has criteria for the evaluation of well location, well characteristics, sampling procedure and sample preservation, analytical method, field quality control, and laboratory quality control. Level 1 data meet the minimum standards for acceptable data while level 5 data are the most defensible. The criteria for evaluating the nitrate and pesticide data are presented in Tables 1 and 2, respectively. The user-friendly format allows the data to be input into a wide range of applications and easily imported into Geographic Information Systems. The Nebraska Department of Agriculture and the Nebraska Department of Environmental Quality provide both direction and financial support for the clearinghouse.