Nitrate is the most common chemical contaminant in groundwater and drinking water in Iowa. This study will provide a cost-effective method for surveillance of nitrate contamination of private drinking-water supplies that can be used for exposure assessment, epidemiological studies, and monitoring of nitrate contamination over time. The University Hygienic Laboratory database of private well-water analyses (approximately 10,000 nitrate analyses/year) will be related to the Iowa Groundwater Vulnerability Regions (GVR) using the IDNR Geographic Information System. Zip-code areas will be spatially related to the GVR units and then the UHL water-quality data will be summarized by zip-codes, by GVR unit, by well depth, and by year. This will provide a sensitive analytical tool to assess spatial and temporal differences in water quality. It is proposed that this approach be used to develop an annual report of water-quality trends in Iowa, summarizing exposure and resource implications.