Neuronavigation has become an established technology which provides objective data for localization in 3D space and thus decreases uncertainties regarding tumor localization, relation to vasculature, safe trajectories, and craniotomy design during surgery. We have evaluated whether neuronavigation based purely on 3D ultrasound without any preoperative navigational imaging can provide necessary information for navigation and resection control. This application is a new way of utilizing ultrasound-guided neuronavigation. Eighteen patients were operated on with ultrasound-based navigation only; they represented 16% of all the 131 navigation-assisted procedures during our 1-year study period. Of the procedures, 2 were planned as diagnostic biopsies, 1 was resection of an abscess, and 15 were tumor resections. Pre- and postoperative radiological images were evaluated to assess volumes and volume reduction following surgery. Pathology results were recorded. For patients undergoing resections, the resection radicality was >99% in 12 patients and 95-99% in 4 patients undergoing resections. In the latter patients, additional radicality was avoided intentionally because of concern for sensitive central structures. The two biopsies yielded representative material. It was possible to use operative neuronavigation based on intraoperative ultrasound without relying on preoperative navigational imaging. Neuronavigation based solely on intraoperative ultrasound was feasible and may increase surgical safety when preoperative neuronavigational image is not feasible or unavailable.