A method for cooling x-ray tubes was devised, based on the principle of relative motion between the target and focal spot. The electron beam is deflected by a rotating magnetic field so that the focal spot moves in a circle upon the target face. Simultaneously, the tube itself is gyrated (without rotation about its axis) so that any point on the target describes an equal circle. The two rotations are equal in frequency but phased 180 degrees from each other. Thus the focal spot remains stationary in laboratory space. The advantages are (1) it is adaptable to most x-ray tubes with target face perpendicular to the tube axis, and target diameter twice that of the longest focal spot dimension, without any modification of tube design; (2) it combines the benefits of a rotating target, water-cooled target, and line focus without the need for rotating joints or vacuum connections. Tubes, operating continuously for hours at a time at a gyrating frequency of 6 r.p.s. have been cooled successfully by this method without observable shifting of the focal spot in laboratory space.