Gas- and particle-phase emissions from gasoline and diesel vehicles operated on chassis dynamometers were collected using annular denuders, quartz filters, and PUF substrates. Quinone species were measured using -(2,3,4,5,6-pentafluorobenzyl)hydroxylamine derivatization in conjunction with gas chromatography-mass spectrometry and highperformance liquid chromatography-mass spectrometry. Nine quinones were observed, ranging from C6 to C16. Newspecies identified in motor vehicle exhaust include methyl-1,4-benzoquinone, 2-methyl-1,4-naphthoquinone (MNQN), and aceanthrenequinone. Gas-phase motor vehicle emissions of quinones are also reported for the first time. Six gasphasequinones were quantified with emission rates of 2-28 000 µg L-1 fuel consumed. The most abundant gas-phase quinones were 1,4-benzoquinone (BQN) andMNQN. The gas-phase fraction was ≥69% of quinone mass for light-duty gasoline emissions, and ≥84% for heavy duty diesel emissions. Eight particle-phase quinoneswere observed between 2 and 1600 µg L-1, with BQN the most abundant species followed by 9,10-phenanthrenequinone and 1,2-naphthoquinone. Current particle-phase quinone measurements agree well with the few available previous results. Further research is needed concerning the gas-particle partitioning behavior of quinones in ambient and combustion source conditions.