Two pickup trucks, both with 5.9 L, turbocharged and intercooled, direct injection diesel engines, were tested for regulated emissions at the Los Angeles County Metropolitan Transit Authority Emissions Testing Facility, one in 1994 and the other in 1995. Emissions testing was conducted using the Dynamometer Driving Schedule for Heavy Duty Vehicles (Code of Federal Regulations 40, Part 86, Appendix 1, Cycle D). Emissions data generated included total hydrocarbons (HC), carbon monoxide (CO), carbon dioxide (CO2), oxides of nitrogen (NOx) and particulate matter (PM). All tests were with a chassis dynamometer capable of transient testing.This paper presents an analysis and comparison of the emissions tests for each year as well as a comparison between years. Differences in emissions found between years are reported. Test methods, procedures and the experimental designs are discussed. The test data presented in this report represents the emissions of three biodiesel fuel blends. In 1995, all fuels were initially tested with the vehicle catalytic converter installed on the vehicle. Subsequent testing was then conducted with the catalytic converter removed from the vehicle. A catalytic converter was not available for the 1994 vehicle.The 1994 tests included both a double arterial cycle of 768 seconds duration and the EPA heavy duty vehicle cycle of 1,060 seconds duration. Rapeseed methyl (RME) and ethyl esters (REE) and blends were compared with a low sulfur diesel reference fuel (D2). In these tests, 100% REE reduced HC (8.7%), CO (4.3%) and NOx (3.4%) compared to 100% RME. The 1994 tests resulted in reductions of HC (52.4%), CO (47.6%), NOx (10.0%) and increases in CO2 (0.9%) and PM (9.9%) for the average of REE and RME compared to diesel.The 1995 tests included only the EPA heavy duty cycle. Fuels used in 1995 were low sulfur diesel reference fuel, 100% REE, and blends of 20% REE-80% diesel and 50%REE-50% diesel. The 1995 tests resulted in reductions in HC (63%), CO (33%), NOx (10%), CO2 unchanged and increases of PM (30%) for 100% REE compared to D2. The catalytic converter had an affect on only the HC and PM. It reduced HC for diesel 10.5% and for REE 13.6%. It also reduced PM for diesel 45% and for REE 56%.