Frequent serious technical errors in mammorgraphy proved to be due to incomplete outlining of the breast, underexposure and blurring. These errors are in most cases secondary to incorrect positioning, absence or improper adjustment of automatic exposure system, insufficient quality of x-ray tube, and use of inappropriate films. Each mammogram should be exposed in such a way so that the film reading can be done using a bright halogen lamp and a twofold magnifying glass. Grain, blurring and artefacts should not interfere with the visibility of diagnostically important details such as microcalcifications of the size of about 0,1 mm.