This fact applies to a wide range of actual technological developments. The use of increasingly hard materials like fine- grained cemented carbides or ceramics requires extraordinary care concerning thin surface layers where even small defects can initiate brittle fracture. Optimized machining processes and delicate surface analyses must be applied. It has been demonstrated recently that residual stresses in surface layers of only few µm thickness reveal significant influence on the bending strength of brittle materials. Hard coatings for cutting and forging tools are widely applied and give rise to the development of refined coating processes. A wide field of coating problems arises in manufacturing components in micro electronics as well as in micro mechanics. In all cases mentioned above, it is well accepted that the residual stresses occurring in the surface layers or coatings can influence the mechanical, tribological, electrical, corrosive, and magnetic properties of the respective component. Therefore, they must be considered during manufacturing and application. Residual stress analysis by X-ray diffraction has proved to be a valuable tool for their determination in crystalline materials since the penetration depth of the monochromatic X-rays used is very shallow. This paper describes actual developments in X-ray residual stress analysis which are going on in analyzing residual stress states with gradients up to several 1000 MPa/µm and in analyzing residual stress states in coatings of less than One m thickness. The advantages and limits of parallel X-ray beam techniques and of grazing incidence of the X-rays are pointed out.