The primary objective of this study was to determine the effect of aromatic compounds in gasoline on exhaust emissions of benzene. Previously reported studies have shown that benzene emissions correlate well with fuel content of benzene and total aromatics. The intent was to determine the relative significance of the individual aromatic species as benzene precursors.Although benzene combustion exhaust emissions were of primary interest, emissions of other aromatic species were also measured. The experimental design enabled determination of fuel composition effects on emissions of benzene as well as other aromatics.A matrix of 16 fuels was formulated with systematic variation in their content of benzene, toluene, ethyl benzene, xylenes, and C+9 aromatics. The emission levels of these species were determined in both engine-out and tailpipe-out exhaust from four 1985/86 model year vehicles. The EPA Federal Test Procedure (FTP) was used in all four experiments.Results show that the exhaust emission rate of each aromatic component is highly correlated with the level of that component in the fuel and, to a lesser degree, with the content of the other aromatics in the fuel. Comparison of tailpipe-out emissions with engine-out emissions indicates that there were no marked differences in catalyst efficiency for the aromatic compounds included in this study.