Ambient air quality data collected by states and local agencies are used in planning the nation's air pollution control strategy, in determining if National Air Quality Standards are being achieved, and in determining long-term trends of air quality. Prior to the regulations of May 10, 1979, the procedures used in site selection, controlling equipment, and calculating and validating data varied considerably among agencies. To alleviate this problem the May 10, 1979, regulations imposed uniformity on the data collected and required precision and accuracy to be reported. This report covers the first year of collecting for precision and accuracy data from state and local monitoring agencies. The data are summarized first by state and pollutant, and then summarized by region and the nation. A brief comparison of the precision and accuracy from the Precision and Accuracy Reporting System and that from the independent performance audit program conducted by the Environmental Monitoring Systems Laboratory is presented.