The Minnesota Bioindicator Study is a long-term field research project. It has three main objectives: (1) to develop a biological system to indicate the spatial and temporal distribution of air pollutants; (2) to determine the effects of air pollutants on important agronomic and forest species; and (3) to archive biological and environmental data, including samples of soil and plant material for future elemental analyses. Ten field plots were established throughout the state and planted with a variety of commercial and non-commercial plant species. Plants were grown in one or more of three different soil regimes. Plant growth and symptom data were collected during the growing seasons of 1983–1987. Air pollutant and weather data were obtained from local and national agencies. No symptoms of sulfur dioxide injury were confirmed, but symptoms of ozone injury were observed in all five years on milkweed, soybean, and/or potato. Preliminary analyses do not indicate statewide effects of ozone on alfalfa yield. About 2000 samples of soil and plant material are stored, and 1.75 million data points have been accumulated. Data from this study are to provide a baseline for documenting long-term changes in the quality of Minnesota's environment.