The first goal of this Dagstuhl Seminar is to survey existing uses of any kind of XR technologies in the OR. More importantly, we will seek to foster and create ideas for novel research on using XR in the OR. This should lead to novel use cases of the technology, novel research questions, and an agenda for research on XR in the OR for the next 5 years. As one of the tangible outcomes, we plan to develop a position paper outlining this agenda during the seminar, and submit it to a major journal. These goals will be achieved by bringing together researchers from all sub-fields of XR (VR, AR, sound and haptic rendering, new materials, and other kinds of mixed reality), along with practitioners (surgeons) from different medical areas, in order to bring the practical perspective of surgery to the seminar.