The phase equilibrium diagram for the TeO2-TeF4 system has been established. Two new compounds, Te2O3F2 and TeOF2, have been identified and characterised by X-ray analysis. Quenching of the liquid allows glasses to be formed in the fluorine-rich part of the system (25% to 83%). The glasses exhibit very low glass transition temperatures ranging from 185 degrees C to - 5 degrees C for the TeF4-rich compositions.