Among the basic problems associated with the development of a gas-turbine plant to use pulverized coal are those related to the burning of the pulverized coal under gas-turbine conditions. These conditions include high heat-release rates, high excess air, high static pressures, and a wide range of variation in all operating conditions. No previous data indicating the effects of pressure on the reaction rate of pulverized coal were available at the start of this investigation, and there had been little occasion to burn pulverized coal at the high heat-release rates used in gas-turbine practice when burning liquid fuels. This paper presents results obtained in a study of the effect of pressure upon the combustion reaction, and describes tests made with four small air-cooled combustors operated at high heat-release rates and low pressure in connection with a small gas-turbine unit. The work described was sponsored by the Locomotive Development Committee of Bituminous Coal Research, Inc., under J. I. Yellott, director of research. It was one of several projects, related to the development of the coal-burning gas-turbine locomotive, which have been assigned to a number of universities and research institutions, and which have been described by Yellott in a recent paper. At the present time, large-scale development work is under way both at Battelle, where full-scale atmospheric-pressure combustors are under test, and at the Dunkirk, N. Y., plant of the American Locomotive Company, where full-scale coal-preparation equipment is being operated with a ⅓-scale combustor at full pressure.