Tailpipe and evaporative emissions from three pre-1985 passenger motor vehicles operating on an oxygenated blend fuel and on a nonoxgenated base fuel were characterized. Emission data were collected for vehicles operating over the Federal Test Procedure at 40, 75, and 90 F to simulate ambient driving conditions. The two fuels tested were a commercial summer grade regular gasoline (the nonoxgenated base fuel) and an oxygenated fuel containing 9.5 percent methyl ter-butyl ether (MTBE), more olefins, and fewer aromatics than the base fuel. The emissions measured were total hydrocarbons (THCs), speciated hydrocarbons, speciated aldehydes, carbon monoxide (CO), oxides of nitrogen (NOX), benzene, and 1,3-butadiene. This study showed no pattern of tailpipe regulated emission reduction when oxygenated fuel was used. THC, CO, benzene, and 1,3-butadiene emissions from both fuels and all vehicles, in general, decreased with increasing test temperature, whereas NOX emissions, in general, increased with increasing test temperature.