FTP-UDDS (urban dynamometer driving schedule) exhaust particulate matter (PM) emission rates were determined for 361 light-duty gasoline (LDGV) and 49 diesel passenger vehicles ranging in model year (MY) from 1965 to 1997. LDGVs were recruited into four MY categories. In addition, special effort was made to recruit LDGVs with visible smoke emissions, since these vehicles may be significant contributors to the mobile source PM emission inventory. Both light and heavy-duty diesels where included in the passenger diesel test fleet, which was insufficient in size to separate into the same MY categories as the LDGVs. Vehicles were tested as-received in three areas: Denver, Colorado; San Antonio, Texas; and the South Coast Air Quality Management District, California. The average PM emission rates were 3.3, 79.9, 384 and 558 mg/mi for 1991-97 MY LDGVs, pre-1981 LDGVs, smoking LDGVs and the diesel vehicles, respectively. Particle size measurements show that most of the mass is present in particles smaller than 2.5 μm. Particle number emission rates were similar for gasoline and diesel vehicles. PM chemical analyses were performed on a subset of samples from vehicles at each location. The PM is largely carbonaceous material. The organic fraction of the carbonaceous material is lowest for diesels and the newer gasoline vehicles and highest for smoking gasoline vehicles. Average sulfate emission rates for gasoline and diesel vehicles were 0.64 and 1.81 mg/mi., respectively. The average trace element contribution to the PM mass was 8.5, 4.2, and 1.2 %, respectively, for the 1991-97 LDGVs, pre-81 LDGVs and the diesels. Individual polynuclear aromatic compounds, steranes and hopanes were measured as well. These data will be used to improve the on-road mobile source PM emissions inventory.