The kinetics of the cristobalite transformation are reported for sintered silica glass from 1200 degrees C to 1650 degrees C and plotted as a time-temperature-transformation diagram. The 1200 degrees C-1350 degrees C transformation data were fit to the Johnson-Mehl-Avrami- Kolmogorov expression with an time exponent of 3.0 +/- 0.6 and an apparent activation energy of 555 +/- 24 kJ/mol for the kinetic constant. The temperature of maximum transformation rate was found to fall between 1500 degrees C and 1600 degrees C. Seeding amorphous silica powder with cristobalite resulted in accelerated transformation kinetics. Silica glass powder containing residual quartz had faster transformation kinetics than fully amorphous powder seeded with cristobalite.