The exhaust emission characteristics of three prototype low-emission vehicles were investigated using standard tests. All vehicles were full sized luxury type with large displacement engines, equipped with an automatic transmission and air-conditioning. Vehicle no. 1 used a modified choke system, exhaust gas recirculation, air injection, a single catalytic reactor, and a charcoal canister to collect unburned hydrocarbons from the exhaust during the cold portion of the test. Vehicle no. 2 also had a modified choke, exhaust gas recirculation, air injection, and two catalytic reactors. Vehicle no. 3 used similar choke modifications and exhaust gas recirculation. This vehicle was equipped with air injection and a catalytic reactor. The following tests were performed: (1) Standard 1970 Federal test procedure for exhaust emissions (FTP); (2) Closed, constant volume sampling technique using nine repeats of the Federal emissions test cycle (9X7); (3) Closed, constant volume sampling technique using the LA4-S4 driving schedule as developed for 1972 and later testing. All three vehicles showed considerable emission reductions relative to present production vehicles. It is expected that a considerable driveability loss could be expected based on dynamometer evaluations.