The standard establishes uniform methods for checking image quality constancy. It describes constancy checking in radioscopy and photography with X-ray image intensifiers. Testing the constancy of governing characteristics of both methods enables conclusions to be drawn on the constancy of the image generating system. In radioscopy, the resolving power, the contrast, the effective radiation field, and the dose rate are used as characteristics, in photography the optical density, the resolving power, the contrast, the effective radiation field, and the dose. A test device is described; permissible limit deviations are stated for this. Other testdevices are permissible provided they fulfil the conditions required in the standard; the determination*of the permissible limit deviations for such "other test devices" is also stated.*The standard should place the user of a diagnostic X-ray unit in a position to be able to check himself regularly the constancy of the material-dependent and equipment engineering-enduced image quality according to the forthcoming modification amendments of the German X-ray regulation.