Two methods for measuring Diesel exhaust particulate emissions are investigated and compared in this study. Total particulate matter emissions have been determined by a Sierra Instruments Model BG-1 Micro-Dilution Test Stand, while total carbon emissions have been determined by a Rupprecht & Patashnick Series 5100 Diesel Particulate Measurement System. Both methods have been subjected to a detailed error analysis, and optimized to improve repeatability. This paper describes the optimization completed, and compares the two methods after optimization. Emission measurements from a single-cylinder IDI engine and a multi-cylinder TDI engine are used to compare the two methods.