The U.S. Environmental Protection Agency (U.S. EPA) Office of Research and Development (ORD) and the Secretariat of the Environment of Mexico City have been working together for more than fifteen years in the evaluation of the Red Automatica de Monitoreo Atmosferico (RAMA) of the City and State of Mexico. Previously these audits were performed once a year by Mr. Willie McLeod of ORD/NERL (National Exposure Research Laboratory), who retired last year. The government of Mexico City made a request to the agency for the continuation of the external audit of the network, and the Director of the NERL named two new auditors to continue this work in Mexico City for the next three years. The Automatic Atmospheric Monitoring Network (RAMA) is comprised of 32 monitoring stations distributed in the Federal District (21) and Mexico State (11), of which only 14 of these stations were evaluated during the year 2000 audit. These stations contain monitors for measuring and recording/transmitting ambient levels of various combinations of carbon monoxide (CO), nitrogen oxide (NO), oxides of nitrogen (NO-x), nitrogen dioxide (NO2), ozone (O3), and sulfur dioxide (SO2).