The thermal decompositions of two beryllium periodate hydrates, Be(IO4)2·8H2O and Be(H4IO6)2·2H2O, were studied by DTA and TG in the temperature range from 298 to 1073 K, and by DSC from 298 to 723 K. The intermediates of the thermal decompositions were identified via quantitative analysis, IR spectroscopy and the TG curves. The data obtained were utilized to suggest a scheme for the thermal decompositions of the two periodates. Both compounds decompose via an anhydrous beryllium iodate, and the final residue is beryllium oxide.