(J.K.)In this paper the measuring apparatuses of ionizing radiation for the radiation monitoring of NPP Dukovany operation is described. The increase of metrological operations number has been made possible only by a timely reconstruction of the laboratory and by computerization of the measuring procedure and of administrative work which consists mainly of recording of a great number information pieces about the observed measuring apparatuses. There are three working places in the laboratory: 1) irradiation gamma stand with cesium-137 sources; 2) irradiation stand with plutonium-beryllium neutron sources; 3) spectrometric working place. With the regard to the uniqueness of the laboratory operation, all the works in the sphere of hardware as well as software has been implemented by own forces. The equipment of the laboratory makes possible to test metrologically all the radiation monitoring apparatuses used in NPP Dukovany. The quantity of operation of he laboratory of ionizing metrology qualifies the proper functioning of the radiation monitoring system, which directly influences the ensurance of nuclear safety of NPP Dukovany.