Abstract The paper presents a statement of the brake thermal efficiencies that may be obtained from gas turbines of various types, and discusses the possibilities and limitations of these types of heat engines. Calculated performances, with tables of computed values, are given for the following types: (1) Explosion turbine with regeneration, (2) Explosion turbine with regeneration and air cooling, (3) Explosion turbine with regeneration and water injection, (4) Explosion turbine combined with steam turbine operated from exhaust-heat boiler, (5) Explosion turbine combined with steam turbine operated from exhaust-heat boiler, with charge precompression and reduced back pressure, (6) Constant-pressure-combustion turbine with regeneration, (7) Constant-pressure-combustion turbine with regeneration and with cooling of the buckets by steam jets, and (8) Constant-pressure-combustion turbine with regeneration and with steam injection into the combustion space. In the conclusion it is stated that a review of the possibilities of the gas turbine does not give much hope of realization of efficiencies such as would encourage attempts to overcome the many difficulties with which the gas turbine is surrounded. In two appendices are considered the entropy chart for gases and the representation of the proposed cycles on this chart, as well as the fundamental formulas and methods used in the computation of the data included in the tables.