Adhesion of metals to ceramics is an area of extreme importance for packaging of electronic devices. In one of the several adhesion schemes that can be employed to promote adhesion between metals and ceramics, the metal is preferentially oxidized at the interface and there is solid solution mixing between the substrate and the oxidized metal at the interface. An example is the Ni/MgO system. Estimation of the extent of mixing at the interface is often difficult and time consuming. This work describes a simple non-destructive method to estimate the extent of interdiffusion between the oxides using a standard x-ray diffraction measurement. This technique relies on the changes in the peak shapes and positions as a function of the nature and extent of interdiffusion. The technique is precise enough to allow one to estimate interdiffasion coefficients in some oxide/oxide systems. The diffusion and intermixing phenomena in the NiO/MgO system will be examined as an illustrative example.