[en] A short history of the International Commission on Radiation Units and Measurements (ICRU) and its main objectives are presented. They now include the development of internationally acceptable recommendations regarding: (1) quantities and units; (2) procedures suitable for the measurement and application of these quantities (as well as the associated uncertainties); (3) physical data needed in the application of these procedures; and (4) definition of terms and concepts used in radiation therapy. One of the most important actions of the ICRU during the last two decades was its recommendation in favor of the introduction of the SI units (International System of Units) in the field of ionizing radiation. Recently published ICRU reports in the field of radiation therapy are reviewed. Reports 23 and 24 provide recommendations for determining the absorbed dose in a patient irradiated with X or gamma ray beams. High energy electron and neutron beams have been considered in Reports 21 and 26 respectively. Report 31 provides a survey of the available anti W values and Report 29 makes recommendations on dose specification for reporting therapeutic irradiation in external beam therapy