Microfilming of X-ray films has become more topical owing to the amendment of the X-ray regulations. The storage of X-rays as reproductions on an image or data carrier is expressly envisaged as a possibility in the text of the regulation. The quality of transfer must be insured and the copies must be legible. In microfilming, the latitude and the resolution capacity of the microfilm and remagnification are appropriate as parameters of image quality. Testing of seven filming systems shows a major range of variation of both parameters; in some cases, the results led to reexamination of the camera adjustment and developer chemistry. A test of constancy of filming analogous to direct radiography appears necessary. A corresponding norm does not exist at present.