With the passage of the federal Clean Air Act, the automotive industry has a clear assignment to reduce automobile emissions drastically by 1975. The control devices presently available have already reduced hydrocarbons 83%, carbon monoxide 70%, and nitrogen oxides 33%. By 1975, these figures must be 98%, 97%, and 90%, respectively.This paper discusses the devices that have been developed to accomplish the reductions to date, and concludes that in the future the crankcase controls will require little change, that the evaporative controls will require some additional improvement but will not change substantially, and that engine modifications do not have much chance of meeting the 1975 standards without a great deal of supplementation.The author feels two methods are available which may be able to reach the 1975 standards: use of manifold reactors and use of catalysts. However, both present problems of materials and thermodynamics, due to high exhaust temperatures. This is the engineering challenge in the next five years.