Abstract: A combustor for gas turbines includes a stepped cylindrical tube defining first, second and main combustion spaces. Primary air supply openings are formed in the tube portion defining the first combustion space, secondary air supply openings in the tube portion defining the second combustion space, and diluting air supply openings in the tube portion defining the main combustion space. To achieve effective cooling of the combustion gas within the combustion chamber, particularly in the second combustion space, and especially in the central portion thereof, and at the same time to maintain a stable combustion, the tube is formed so, and the cross-sectional areas of the primary, secondary and diluting air supply openings are dimensioned so, that 25 to 32% of the total amount of air supplied to the combustion chamber are used as primary air in the first combustion space, 38 to 50% as secondary air in the second combustion space, and less than 30% as diluting air in the main combustion space.