The morphology of thermally induced oxygen precipitates in Czochralski silicon crystals and its dependence upon oxygen supersaturation were investigated using transmission electron microscopy. The morphology of oxygen precipitates depends not only upon the annealing temperature but also on oxygen supersaturation. On the other hand, the oxygen precipitates near the denuded zone are octahedral, independent of the annealing temperature used, which demonstrates the important role oxygen concentration plays in morphology.