The paper summarizes the 1991 Symposium on Stationary Combustion NOx (nitrogen oxides) Control, held March 25-28, 1991, in Washington, DC. Approximately 500 attended, representing 53 domestic and 13 foreign utility companies, federal and state government agencies, research and development organizations, and equipment vendors. Sixty-six presentations were made. The symposium focused on new results and understandings since the previous (1989) symposium, as they pertain to electric utility power plants and other boilers burning coal, oil, and gas. Key points included the significant increase in full-scale retrofit demonstrations of low-NOx combustion systems in the U.S. and abroad over the past 2 years; full-scale operating experience in Europe with selective catalytic reduction (SCR); pilot- and bench-scale SCR investigations in the U.S.; increased attention to selective noncatalytic reduction (SNCR) in the U.S.; and NOx controls for oil- and gas-fired boilers.