Exhaust emission rates of selected toxic substances were determined for two late model gasoline-powered passenger cars. These substances are listed, or are under review for listing, as toxic air contaminants under California's air toxics program and include volatile and semi-volatile halogenated hydrocarbons, 1,3-butadiene, acrolein, phenols, nitrobenzene, dialkylnitrosamines, and a number of other unregulated emissions. Regulated gaseous emissions and fuel economy were also measured. A literature search was performed to determine if any of these compounds had previously been measured in the exhaust of gasoline-powered vehicles and if appropriate analytical procedures were available. When unavailable, procedures were developed for sampling and analyzing the unregulated toxic emissions. The two vehicles were then tested to determine the emission rates of the targeted compounds. In the tests, a 1987 Ford Taurus equipped with a 3-way plus oxidation catalyst and a 1986 Toyota Camry equipped with a 3-way catalyst only were operated over the Federal Test Procedure, the Highway Fuel Economy Test, and the New York City Cycle. The test fuel was a regular unleaded gasoline without ethanol or methanol, and was obtained from California.