The crystal structure of anatase was refined at several temperatures between 25 °C and 800 °C using single-crystal x-ray diffraction data. The only structural parameter, the z coordinate of oxygen, changes regularly from 0.2081(2) at 25 °C to 0.2076(3) at 800 °C.This change is about an order of magnitude smaller than that proposed by Horn and Schwerdtfeger (1971) to explain the temperature dependence of electron paramagnetic resonance spectra of anatase. The thermal vibrations of the titanium ions are isotropic, those of the oxygen ions highly anisotropic. That these thermal displacements may produce appreciable corrections to the bond-length calculations is discussed. © 1972, Walter de Gruyter. All rights reserved.