The development of a Geographic Information System (GIS) application to evaluate potential environmental hazards within the Bushkill watershed in Northampton County, Pennsylvania, is described by the authors. Information identifying hazardous materials used by businesses within the watershed was obtained from databases of the Environmental Protection Agency. These databases were supplemented and updated by visual reconnaissance and by a review of current tax maps, zoning information and aerial photographs. Information regarding the use or storage of substances considered hazardous was collected from various agencies as well as any known violations of environmental regulations by the businesses. Geographic information including remotely sensed data and maps of surface water bodies, geology and soil types was also obtained for the study area. A GIS was used to integrate the geographic information with the hazardous substance database resulting in a tool for use in environmental site assessments, planning for subsequent site characterization, and for environmental educational purposes.