Abstract: A method of casting a blade or vane for a gas turbine engine which enables the production of more complex internal shapes than those which may be made by prior art methods. The method of the invention includes the steps of:making a temporary filler piece from a disposable material,holding the filler piece in place in a die,injecting the core material into the die and causing it to solidify round the filler piece,removing the core from the die,causing the filler to be removed from the core to leave within the core a cavity having the shape of the filler, andusing the core thus produced in an investment casting process to form the blade or vane shape.