[en] Thirteen radiotherapy departments in the Netherlands and Belgium participated in an intercomparison of the calibration procedures in use for the quality control of iridium-192 high dose rate sources. A measuring device from 1 of the departments was taken to the 12 other participants, where 1-3 sources were measured by both the local and the visiting physicist's team. Also, 1 ¹⁹²Ir HDR reference source was taken to 7 other - Dutch - departments to serve as a stability check of the measuring device. The results of the local calibration were compared with the values obtained by the visiting team. A mean deviation of +1.3% was found in 19 observations, with values ranging from -0.4% to +3.0%. In total, 16 sources were checked. The measured reference air kerma rate of the available sources was compared with the value stated on the source calibration certificate: the values on the certificate were on the average +1.8% higher than the measured values, ranging from -4.2% to +6.8%. In 1 instance the reference source was also measured by The Netherlands Measurements Institute (NMI), the national standards laboratory in the Netherlands. A good agreement was found between the NMI calibration and the reference air kerma rate determined with the measuring device used in this project