The Aerometric and Emissions Reporting System (AEROS) is a comprehensive computer-based system established by the National Air Data Branch to collect, store and analyze air pollution data. The data are collected by the various state and local agencies and reported to EPA. These data are then stored and analyzed in AEROS. The most noteable feature of AEROS is that it is a reporting system. The primary function of AEROS is to provide concise and standardized reports on various aspects of air pollution. AEROS is composed of several subsystems, some of which are capable of functioning as independent data systems. The intent of this pamphlet is to show the relationships between the various AEROS subsystems and the information available from each.