The Nebraska Quality-Assessed Agrichemical Contaminant Database (NQAAC) contains groundwater nitrate and pesticide data collected from wells. Types of wells sampled include domestic, irrigation, livestock, commercial/industrial, and monitoring wells. Samples were collected by a variety of agencies, analyzed by certified laboratories, and submitted for inclusion in the database. Upon submission, data are screened for essential elements and assigned a quality flag between 1 (low) and 5 (high). Wells represented in the database have variable sampling histories, with the earliest results dating to 1974. Maintenance of the database is a partnership between the Nebraska Department of Environment and Energy, the Nebraska Department of Agriculture, and the Conservation and Survey Division.