The paper gives results of an evaluation of nitrogen oxide (NOx) emission control catalysts commercially developed for power plant selective catalytic reduction (SCR) installations. With the objective of establishing the performance of SCR catalysts and related technology, control at the 85% removal level was achieved with sulfur dioxide (SO2) present. In the absence of SO2 and under optimum conditions, greater than 99% removal was possible. (Ammonia slip was not measured.) Several SCR catalysts were tested under different operating conditions. The effects of NH3/NO ratio (0.1/1.0), space velocity (3,000 - 8,000 h to the -1 at STP), and temperature (270 - 400 C) on reaction kinetics are reported. The target NO concentrations were 500 and 1000 ppm. Particular emphasis was on investigating the poisoning effects of SO2 on the SCR catalysts due to the significant sulfur content in U.S. coals. It was confirmed that, while SO2 may exhibit poisonous effects on some catalysts, the commercial catalysts designed for the high- and low-dust SCR installations show high resistance to SO2 poisoning.