Diesel particulate and gaseous emissions, fuel economy, and mutagenic activity of the particulate extracts were measured for 22 light-duty diesel vehicles representing 1979 through 1982 model-year production of domestics and imports. These vehicles were operated on a chassis dynamometer in a temperature controlled environment. The objectives of this study included measuring effects of fuel aromaticity [0 to 37%], ambient test temperature [25, 50, 75, and 100°F], and vehicle duty cycle on particulate emissions and associated biological activity.Results of this investigation showed that ambient temperature environmental changes on the operating vehicle had virtually no effect on particulate and mutagenicity measurements. Increasing fuel aromaticity in three test vehicles did not show a definitive relationship of particulate level versus fuel aromaticity. The influence of driving cycle on particulate emissions showed the particulate level and mutagenic activity were greater with the New York City Cycle than either Federal Test Procedure cycle or Highway Fuel Economy Test cycle. Mutagenic assessment of particulate extracts which had been separated into six HPLC fractions showed 90+ percent of the direct acting mutagenicity was contained in three of the six fractions.