A shutter for an x‐ray beam consists principally of a rotary disk with alternate open and opaque sectors, and a suitable control mechanism operated by an electromagnet. Several exposures may be made for one winding, a feature of convenience when remote control is desired. The motion of the disk is the same for opening and closing so that each part of the beam is turned on for the same length of time. The shutter will accommodate an x‐ray beam directed anywhere between the vertical and the horizontal.