In this study, a Cummins B5 diesel engine was set up to operate on a dynamometer under the US transient cycle. Twenty-four diesel fuels were tested. Regulated air pollutants (HC, CO, NOx, particulate matter) and polycyclic aromatic hydrocarbon (PAH) emissions were measured. PAH was analyzed by gas chromatography/mass spectrometer detector (GC/MS). The average emission factors were 0.32, 2.1, 4.9 and 0.09 g/BHP-hr for HC, CO, NOx and particulate matter, which were all lower than the emission standards in Taiwan. Total PAH (sum of 21 PAHs) emission factor was 3.6 mg/BHP-hr. The non-liner two-variable regression analysis was used to identify the fuel properties which may have influenced the diesel engine particulate and PAH emissions. The greatest influential factor on particulate emission was carbon content, followed by density and viscosity. A 1% increase in carbon content was associated with an increase of 63.1% in particulate emission. The first three important fuel properties affecting PAH emission were density, viscosity and carbon content. The influences of total aromatics and polyaromatic content on particulate and PAH emissions were insignificant.