Abstract: An improved diffusion bonding fixture for holding workpiece surfaces in opposed contacting relation and exerting controlled pressure across the surfaces is disclosed. The fixture includes components having different thermal expansion characteristics which hold the workpiece surfaces together and generate pressure on the surfaces upon heating to the bonding temperature. The fixture also includes one or more pressure-controlling shim members disposed between the components of the fixture, the shim members being selectively and controllably deformed by the expanding components to control said bonding pressure at the desired value and to prevent unwanted distortion of the workpiece surfaces and fixture components. The fixture is especially useful in bonding workpiece surfaces of highly complex configurations, such as those associated with gas turbine blades, vanes and the like.