The problem addressed in the report concerns the control of emissions from motor vehicles and particularly the actions which may be taken before these motor vehicles are released by the manufacturers to the public. NAPCA exerts its main point of control at the prototype stage, by issuing certificates for engine prototypes which pass certain criteria when subjected to a standard test procedure. The major requirements are on the level of carbon monoxide (CO) and hydrocarbons (HC) in the exhaust. The Secretary of Health, Education and Welfare has been authorized to test new vehicles or engines being manufactured to determine if they are in fact constructed in all material respects substantially the same as the certified vehicle or engine. The study has been conducted to assemble meaningful information concerning motor vehicle assembly line testing for assisting policymakers in planning courses of action. Assembly line testing is herein projected as a program in quality control and assurance having two essential parts: the control and assurance program carried out by the manufactureres and the audit and monitoring function carried out by NAPCA. The planning, the development, and the implementation of both parts of the projected program are presented.