The paper covers highlights of SAE activity on emissions control from the early efforts of Campbell and others in the 1930's to the present time. Evidence of substantial involvement in the Los Angeles “smog” composition led to the development of analytical tools for continuous evaluation of exhaust. With these tools and other basic information, it became possible to develop many control devices.Over 20 of these devices have been added as standards have tightened. The negative result has been increasing cost and complexity. The crankcase and evaporative systems have been controlled, but the principal emissions have come from the exhaust, and therefore most of the controls were directed to this source.Combustion within the engine has been the principal area of attention, but when this did not meet the requirements of the existing statues, combustion beyond the exhaust ports became important. Notable contributions to this art were air pumps, afterburners and catalysts.The thermodynamic and other considerations involved in the use of these devices are covered. The present situation as affected by smaller, lighter vehicles and extensive use of electronics is described.Recent cost and benefit estimates are reviewed. These appear to indicate that the benefits of the present, highly complex systems are far outweighed by the costs. Some suggestions for dealing with this situation are made.