The structure of BiVO4has been determined by the Rietveld method at 300, 573 and 898 K and confirms the space group of the ferroelastic phase as 12/a and that of the paraelastic phase as 141/a. The displacement vectors of the atoms involved in the switching of ferroelastic states are calculated and indicate that the Bi displacements are the controlling factors in'the process. An analysis is given of the eigenvectors of the Bgmode responsible for the transition. © 1979, Taylor & Francis Group, LLC. All rights reserved.