This standard deals with the constancy tests of functional performance characteristics of medical electron accelerators supplying X-ray and electron radiation with nominal energies in the range of 1 MeV to 50 MeV with a highest absorbed dose rate between 0,001 Gy×s-1 and 1 Gy×s-1 in 1 m exposure distance and for normal exposure distances (NBA) between 50 cm and 200 cm. It indicates test frequencies to be adhered to at minimum in order to be able to determine changes to these characteristics in a timely manner. The definition of functional performance characteristics of medical electron accelerators as well as the test methods and test conditions to be used for the type and acceptance tests are specified in standard DIN EN 60976. Some of the test methods in DIN EN 60976 are simple enough to be directly adopted as a constancy tests. The standard does not include safety characteristics (such as, for instance, switching-off functions) as the test for these is specified in DIN EN 60601-2-1. This standard has been prepared by Working Committee NA 080-00-05 AA "Strahlentherapie" ("Radiotherapy") at the Radiology Standards Committee (NAR).