Thermal stability and high-temperature degradation of pristine bisazafullerene (C59N)(2) were analyzed by infrared and Raman spectroscopy in the temperature range from 300 to 745 K. The spectra showed a reversible temperature dependence up to 550 K. For higher temperatures an irreversible degradation into disordered graphite was found. Approximately 55% of the material resisted a thermal treatment of 745 K for several hours. A mechanism involving a low stationary concentration of C59N. monomer radical species and a slow graphitization is proposed for the thermolysis of the material. The remarkable thermal stability of pristine bisazafullerene (C59N)(2) is ascribed to the low stability of the C59N. monomer radical species, the high activation energy for graphitization, and the absence of other reaction partners under high vacuum conditions.