Particulate matter (PM) emitted from light-duty gasoline powered vehicles is under increasing scrutiny due to potential adverse health effects and on ever increasing number of vehicles in the fleet. In this program, a group of California ULEV II and SULEV II certified light-duty gasoline vehicles were tested for PM mass and number emissions and compared with older model LEV I certified gasoline vehicles under the Federal Test Procedure (FTP) test cycle. PM mass and number emissions were collected from a Constant Volume Sampling (CVS) full dilution system. PM mass samples were collected with the gravimetric method. Filter conditioning and weighing procedures are in compliance with the Code of Federal Regulations (CFR) Part 1065. Total particles (solid and volatile) were measured using multiple fast response particle counting instruments including a TSI Engine Exhaust Particle Sizer (EEPS) and two Condensation Particle Counters (CPC).Test results show that PM mass and number emissions from both LEV I and LEV II vehicles are highest during engine cold starting. After the engine is warmed up, PM mass and total particle number are reduced significantly, and PM mass is reduced to near background levels. PM mass emissions from LEV II vehicles are significantly lower than from older LEV I vehicles in phase 1 of the FTP cycle. Test results also indicate total particle number emissions measured from the current sampling method appear to be repeatable and the Coefficient of Variance (COV) for particle number measurement is lower than the COV from the filter-based gravimetric method at very low PM emission levels for LEV II vehicles.