A study was conducted in 1971 to assess the overall effects of lead additives in gasoline on the performance, durability, and costs of emission control devices/systems which might be used to meet the 1975-1976 federal emission standards for light-duty motor vehicles. Although no system has yet demonstrated meeting the 50,000-mile emission level lifetime, all currently planned 1975-1976 emission control systems include a catalytic converter. However, lead additives are toxic to catalytic materials; they reduce catalytic activity, which results in increasing emission levels with mileage accumulation. Unleaded gasoline would be required in quantities sufficient to satisfy the demands of vehicles equipped with a catalytic converter in order to prevent catalyst activity degradation from lead additives. Implementation of such advanced emission control systems implies very high cost to the consumer, with the cost being a strong function of the required NOx emission level. At this time, estimated overall costs to the consumer (initial, maintenance, and operating) for emission control systems being considered for the 1976 federal emission standards are $860 above average 1970 vehicle costs, over an 85,000-mile vehicle lifetime. This estimate is based on a system incorporating a dual (HC/CO, NOx) catalytic converter, a low-grade rich thermal reactor, and exhaust gas recirculation. This system is currently considered to have the most promise to meet the 1976 NOx standard of 0.4 g/mile.