This book contains the combined papers from a NATO sponsored meeting entitled "Mobile Source Emissions Including Polycyclic Organic Species". This meeting was held in Liege, Belgium, from August 30 to September 2, 1982, as an Advanced Research Workshop (ARW). Specialists from 13 countries met to discuss the impacts of fuel type and engine operation on emissions from gasoline and diesel-powered vehicles. The meeting was organized into five sessions: basic studies, biological activity, analytical methods, data bases, engineering and international research programs. The five sessions were each followed by intensive discussions on the important conclusions to be drawn from the data presented. From these session discussions, subcommittee efforts and a final group discussion on all the research results presented, a meeting summary was prepared by the editors that presents the major findings of the conference and gives detailed recommendations for future research. This summary is included at the end of the book. The summary i"nc1udes highlights of data presented, areas of research needs, recommendations for standardization of test parameters and species analyzed, suggested new methodology for characterizing mobile emissions, trends in fuel use including diesel, gasoline, anti-knock additives and blending agents, operation of catalysts, control strategies, implications from both in vivo and in vitro health effects studies, and a presenta tion of the scopeiand direction of several large international programs that are major studies of mobile source performance.