The Michigan-Ohio District Office of the Environmental Protection Agency was contacted in April, 1975 by a person living in the Cleveland, Ohio area about the unpleasant odor emanating from his brand-new 1975 catalytic converter-equipped Plymouth Gran Fury. The odor had been noticeable from the time the owner took delivery of the car, and was at its worst when the car was idling or moving in dense traffic, according to the owner. Along with the unpleasant odor, irritations of the throat and nose were experienced by the owner and his family. District Office personnel contacted the Emission Control Technology Division for technical advice on the problem. The owner was invited to bring his car to the Motor Vehicle Emission Laboratory (MVEL) for a thorough investigation. This report covers that investigation, which took place in early June, 1975.