Abstract: A gas turbine engine having a compressor and a combustion chamber, a supply of liquid hydrogen, and means for injecting the hydrogen in a cryogenic state into the intake of the compressor or into the compressor one or more stages downstream from its intake. Some of the hydrogen may also be injected into the combustion chamber. The hydrogen directed to the combustion chamber may be heated by heat from the engine lubricating oil or hot engine components. Hydrogen may be injected into the compressor only at speeds above idle speed. Hydrogen flow to the compressor may remain substantially constant, but hydrogen flow to the combustion chamber may vary over a wide range.