Diesel vehicles are an important source of emissions of air pollutants, particularly toxic compounds with potential health impacts. Current developments in engine design and fuel quality are expected to reduce these emissions, but many older vehicles will make a major contribution to urban pollutant concentrations and related health impacts for many years. In this study emissions of a range of toxic compounds are reported using in-service vehicles driven through urban drive cycles using a range of diesel fuel formulations. The fuels ranged in sulfur content from 24 -1700 ppm, and in total aromatics from 7.7 -33 mass %. Effects of fuel composition on the emissions of a range of toxic species are reported. The toxicity of vehicle exhaust, as determined by inhalation cancer risk and Toxic Equivalency Factor (TEF) – weighted PAH emissions, is reported.