Since 1981 the Environmental Monitoring Systems Laboratory (EMSL) of the Environmental Protection Agency (EPA) at Research Triangle Park, North Carolina has been conducting performance audits of the ambient air analyzers used in the National Crop Loss Assessment Network (NCLAN). These audits provided the NCLAN researchers the means to assess the quality of the data gathered by their respective air monitoring projects. The paper summarizes and reviews the results for all the audits from July 1981 through August 1986. Approximately 288 analyzers were audited and only 9 were found to be outside the NCLAN's acceptable goal of + or - 15%. Approximately 185 ozone, 81 sulfur dioxide, 18 oxides of nitrogen, and 4 carbon dioxide monitors were audited.