Abstract: An apparatus for checking the in-register bearing of a printing plate on the plate cylinder of printing machines possesses measuring sensors in the tension rail receiving the printing plate, by which the in-register position can be detected in the form of electrically scannable signals. Contact faces are mounted in the region of the tension rail so that the signals can be scanned directly by machine control, for example in conjunction with an automatic or manual printing-plate feed. The contact faces are placed in contact with the frame sensing heads which are mounted movably relative to the plate cylinder and which are pressed against the contact faces after an appropriate angular positioning of the plate cylinder. When a new printing plate is introduced, an evaluation unit receiving the signals is coupled to the measuring sensors.