An analytical program has been developed to quantify approximately 250 compounds in gasoline. This program combines four separate gas chromatographic analyses and a preparative liquid chromatographic separation. Benzene, toluene, alcohols, and ethers are determined using standard analyses. Both the gasoline and the saturate fraction from gasoline are analyzed using a customized capillary column analysis. The combined analyses provide for the correction of the possible coelution of benzene and unknowns, coelution of toluene and 2,3, 3-trimethylpentane, coelution of saturates and olefins, and coelution of saturates and aromatics. The results of the combined analyses are presented by individual compound or coeluting olefinic and/or aromatic compounds and by compound types.The final report is used to provide a detailed characterization of gasolines. This is especially useful for studying the effect of compositional changes on emissions and on ozone formation.