[en] A rotating anode X-ray target with improved resistance to deformation is described. It comprises a disc having a focal track layer of X-ray emissive material coating deposited on an annular marginal portion of the disc which is adjacent to the outer peripheral edge. Opposed bevel surfaces converge towards the edge. The layer has one part on one bevel surface, from which X-rays are emitted in use, and a second part which is on the other bevel surface and has a radially inner feather edge. Thus there is an extremely thin terminal edge of the layer having the required thermal expansion and contraction characteristics and mechanical flexibility. The substrate disc is made of, for example, molybdenum or graphite. Variations and method of operation are detailed. (U.K.)