Hydrothermal annealing experiments have been performed on samples of the Sharps meteorite in order to investigate the mechanism responsible for the metamorphism-related, 105-fold range in the thermoluminescence (TL) sensitivity in ordinary chondrites. Duplicate 50 mg samples of meteorite were annealed under the following conditions: (a) 168 h at 785¿C and 1 kbar; (b) the same time, temperature and pressure, but with 2 wt% water; (c) 174 h at 855¿C and 0.77 kbar with 2 wt% water and 2 molal sodium disilicate (NadiSi); (d) the same time, temperature and pressure as the preceding samples, but with 10 wt% H2O and 2 molal NadiSi. Samples annealed under the first three sets of conditions showed little or no change in their TL sensitivities, however the samples annealed with 10 wt% water and 2 molal NadiSi showed a 3 to 10-fold increase in TL sensitivity, and the temperature of the TL peak was suggestive of feldspar in the high-temperature form. We suggest that these data are consistent with the TL sensitivity-metamorphism relationship in ordinary chondrites being due to the formation of the TL phosphor, feldspar, by the crystallization of chondrule glass.