The report gives results of combustion tests of petrofuels and synfuels at EPA's Research Triangle Park (NC) combustion laboratory on a 740-kW (thermal input) package boiler and a 190-kW (250 hp) stationary diesel internal combustion engine. These tests were the first in a series to develop a protocol for determining environmentally significant differences between petrofuel and synfuel combustion emission characteristics. Six petrofuels and four synfuels were evaluated. Particulate samples, obtained using a modified EPA Method 5 train and a dilution tunnel with a filter, were analyzed using Level 1 procedures with emphasis on organic constituents. Results showed that the test and sample collection procedures yielded both inconsistent sample loadings and contaminants that masked the true fuel combustion products. Corrective procedures were identified which will be used in subsequent tests.