This SAE Information Report describes uniform laboratory techniques for employing the constant volume sampler (CVS) system in measuring various constituents in the exhaust gas of gasoline engines installed on passenger cars and light trucks. The techniques described relate particularly to CVS systems employing positive displacement pumps. This is essentially an almost obsolete system relative to usage in industry and government. Current practice favors the use of a critical flow venturi to measure the diluted exhaust flow. In some areas of CVS practice, alternative procedures are given as a guide toward development of uniform laboratory techniques.