This report details the advances that have been made in the control of aircraft gas turbine engine emissions. Two technologies of differing complexities have evolved. The success of the first, which controls only hydrocarbons and carbon monoxide, is attributable to innovations in engine operation, the fuel injection system, and the airflow patterns within the combustor. The simplicity of this system gives it wide applicability. The second technology, capable of controlling oxides of nitrogen, in addition to HC and CO, uses exotic methods of fuel preparation and multiple zones of combustion. A table, which follows the report, summarizes the EPA technical staff's assessment of the prospects of each engine meeting the levels specified in the 1979 standards, based on manufacturers' data. Control strategies for HC and CO should be ready for implementation by 1979-1980, but, due to the complexity of the oxide of nitrogen control systems, and the fact that requisite levels of technology are currently found only in some of the largest T2 12 class engines, the practicality of implementation in T1 and APU classes by 1982 is questioned.