We study brain deformation for a series of 8 resection cases carried out in the interventional MR suite at the University of Minnesota. The pattern of deformation is described qualitatively. We also quantify deformation by identifying anatomical landmarks spread over the brain in pre- and post-resection images, and show these values agree well with the results obtained from an automatic non-rigid registration algorithm. For all but one patient, the deformation was significantly greater ipsilateral to the lesion than contralateral, with the contralateral deformation being of the same order as the precision of the measurements. For the remaining patient, there was bi-lateral deformation of several millimetres. Example deformation fields are shown illustrating the distribution of deformation over the brain. The variability of deformation between subjects was considerable, suggesting the automatic correction of intraoperative deformation without use of interventional images may be difficult to achieve.