Air quality simulation modeling continues to attract widespread attention and plays a critical role in the development of rational approaches for the maintenance of air quality standards. One major aim of the NATO/CCMS air pollution project is to keep the users of models informed as to the current state of the art. Because of the rapid advances in techniques and the diversity of the applications of air quality modeling it has seemed desirable to provide an opportunity for an informal give-and-take exchange of the latest information on modeling and closely related topics. With this objective in mind the participation at the 3rd Meeting of the NATO/CCMS Panel on Modeling, held on 2-3 October 1972 in Paris, France, was widened to include representation well beyond the regular membership countries. All participants were invited to submit in advance extended abstracts in English of the material that they would present. The Minutes of the 3rd Meeting are also included since they provide some additional information of interest and a summary of the meeting.