Radioactivity in one of the natural hazards occurring in Polish mines. Particularly for this hazard the control system should ensure reliable results of measurements. For this purpose internal quality assurance systems are introduced to laboratories dealing with measurements of radioactivity. In the framework of implementation of the quality assurance system the Laboratory of Radiometry of the Central Mining Institute has been involved in two intercomparison systems organized by IAEA and EPA. Those systems deal with measurements of natural and artificial radioactivity of solid and liquid samples. For radon and its daughters similar intercomparisons with many participants, are mor difficult to be carried out. Therefore in such cases bilateral intercomparisons are performed. The presented results of the intercomparisons have pointed out that the internal quality assurance system ensures the obtaining of correct results. On the other hand the intercomparisons permit to check the applied research procedures.