[en] At the year 1998 the Standard of X radiation air kerma and dose equivalent and their rates of the Slovak Institute of Metrology was approved and declared as the national standard. From that time there were observed considerable progress of the measuring techniques and of the measurements, too. That reflected into the several upgrading of instrumentation of this standard and improvement of its metrological parameters. At 2004 was performed the revision of the national standard of air kerma,and dose equivalent of the X radiation and their rates and it was renamed to National standard of X radiation. There have been done the some modifications, upgrading and changing of the basic or auxiliary devices and of the measuring processes. All this modification, upgrading and changing brought the simplification and the improvement to the measurements, to the calibrations and to the tests made with utilisation of the national standard of X radiation. (author)