The thermal properties and devitrification behaviour of new fluoride glasses were determined by means of thermoanalytical techniques. The glass-forming and stability parameters have been defined and evaluated from the measured characteristic temperatures. The kinetics of devitrification of bulk glass samples was investigated by combining data obtained from both isothermal and constant-heating-rate techniques. The kinetic data were also used to construct the time-temperature-transformation (T-T-T) curves and temperature-heating rate-transformation (T-HR-T) curves. These graphical illustrationsemulate the thermal condition of glass preforms while awaiting fibre drawing. The results obtained are compared with a standard fuorozirconate glass currently developed for fibre optical applications. © 1994.