In-vehicle concentrations of selected gasoline-derived volatile organic compounds (VOCs) and formaldehyde were examined on 113 commutes through suburban New Jersey and 33 New Jersey/New York commutes. Overall median concentrations were lowest in a typical suburban commute, slightly higher on the New Jersey Turnpike, and highest in transit through the Lincoln Tunnel. Median in-vehicle concentrations of benzene, ethylbenzene, m&p-xylene, and o-xylene were 14, 6.8, 36, and 15 mu g/m(3), respectively. One vehicle, with a carbureted engine, developed malfunctions that caused gasoline emissions within the engine compartment during driving, resulting in the gasoline-derived VOC concentrations in this vehicle being much higher than in the properly maintained fuel-injected vehicle, particularly for the low ventilation extreme. The highest in-vehicle benzene concentration measured during these malfunctions was 45.2 mu g/m(3). The air concentration in the vehicle driven in tandem was a factor of 25 less (1.8 mu g/m(3)).