A Powder River Basin subbituminous coal from the North Antelope mine and a petroleum shot coke were received from Northern States Power Company (NSP) for testing the effects of parent fuel properties on coal-coke blend grindability and evaluating the utility of petroleum coke blending as a strategy for improving electrostatic precipitator (ESP) particulate collection efficiency. Petroleum cokes are generally harder than coals, as indicated by Hardgrove grindability tests. Therefore, the weaker coal component may concentrate in the finer size fractions during the pulverizing of coal-coke blends. The possibility of a coal-coke size fractionation effect is being investigated because it may adversely affect combustion performance, it may enhance ESP particulate collection efficiency. Petroleum cokes contain much higher concentrations of V relative to coals. Consequently, coke blending can significantly increase the V content of fly ash resulting from coal-coke combustion. Pentavalent vanadium oxide (V{sub 2}O{sub 5}) is a known catalyst for transforming gaseous sulfur dioxide (SO{sub 2}[g]) to gaseous sulfur trioxide (SO{sub 3}[g]). The presence of SO{sub 3}(g) strongly affects fly ash resistivity and, thus, ESP performance.