"Introduction This document presents a detailed description of a research program entitled ""Exhaust Benzene Emissions From Late Model Vehicles"" performed by DMACS Engineering Laboratories (DEL) for the American Petroleum Institute (API). The program entailed testing a fleet of 41 late model vehicles for engine-out@ catalyst-out@ and tailpipe emissions of benzene and toluene as well as all regulated pollutants. There were two test fuels used in this program. Fuel I contained 1.07% benzene by volume. Fuel 2 was prepared by adding two percent by volume of benzene to Fuel 1. The resulting blend contained 2.89% benzene by volume. Each vehicle was tested at least once with each test fuel. The resulting database was then analyzed to evaluate the degree of correlation between benzene emissions and various vehicle parameters@ and to determine the effect of fuel benzene content on exhaust benzene emissions. Since the program was large in scope and the analysis of the data extensive@ this report contains two appendices. Appendix I contains procedural details and data summaries to augment the body of the report. Appendix II@ which has been prepared as a separate volume@ contains all data and analysis in an unabridged format."