The paper presents the results of radiological investigation of several mushroom samples collected in the fall of 2004 in
different parts of Europe. The work was performed in order to support decision making to develop and produce a certified reference
material for quality assurance of radionuclide measurements in environmental samples. The levels of 137Cs in mushrooms varied widely ranging from 0.6 to 4300 Bq/kg on dry mass basis, while those of natural 40K were relatively constant. In one sample 60Co of unknown origin was detected (25±2 Bq/kg dry mass), while 90Sr concentrations were usually below the detection limit (<150 mBq/kg dry mass).