Exhaust emissions were characterized from a Cummins LTA10 heavy-duty diesel engine operated at two EPA steady-state modes with and without an uncatalyzed Corning ceramic particulate trap. The regulated emissions of nitrogen oxides (NOx), hydrocarbons (HC), and total particulate matter (TPM) and its components as well as the unregulated emissions of PAH, nitro-PAH, mutagenic activity and particle size distributions were measured. The consistently significant effects of the trap on regulated emissions included reductions of TPM and TPM-associated components. There were no changes in NOx and HC were reduced only at one operating condition. Particle size distribution measurements showed that nuclei-mode particles were formed downstream of the trap, which effectively removed accumulation-mode particles. All of the mutagenicity was direct-acting and the mutagenic activity of the XOC was approximately equivalent to that of the SOF without the trap. When the trap was used, the particle-associated mutagenicity decreased mainly due to the reduction in the concentration of particles. The trap XOC showed no mutagenic activity. There was some shifting of PAH into the vapor phase when particle emissions were reduced with the use of the trap. Under the test conditions chosen for this engine, the ceramic particulate trap reduced the concentration of emitted particles without increasing the levels of particle-associated mutagenicity, PAH or nitro-PAH.