Abstract It used as the plasma-facing material in the next-generation fusion devices, graphite will induce radioactivity in impurities in the graphite. This study was carried out to evaluate the amount of radiologically significant impurities in commercial isotropic graphite tiles. Special attention is given to the benefits of purification by halogen treatment. Graphite tiles from seven Japanese companies were irradiated in JMTR to neutron fluences up to 7.7 × 10 24 n/m 2 fast ( E > 0.1 MeV) and 1 × 10 25 n/m 2 thermal ( E < 0.683 eV) at about 450 K. Subsequent γ-ray spectroscopy revealed that major impurities contributing to the induced radioactivity are the IIId, IVa, Va elements and rare earth elements. The origins of these impurities are suggested and the effects of halogen treatment on the reduction of these impurities are analyzed.