We report on the first successful intraoperative update of interactive image guidance based on an intraoperatively acquired magnetic resonance imaging (MRI) date set. To date, intraoperative imaging methods such as ultrasound, computerized tomography (CT), or MRI have not been successfully used to update interactive navigation. We developed a method of imaging patients intraoperatively with the surgical field exposed in an MRI scanner (Magnetom Open; Siemens Corp., Erlangen, Germany). In 12 patients, intraoperatively acquired 3D data sets were used for successful recalibration of neuronavigation, accounting for any anatomical changes caused by surgical manipulations. The MKM Microscope (Zeiss Corp., Oberkochen, Germany) was used as navigational system. With implantable fiducial markers, an accuracy of 0.84 +/- 0.4 mm for intraoperative reregistration was achieved. Residual tumor detected on MRI was consequently resected using navigation with the intraoperative data. No adverse effects were observed from intraoperative imaging or the use of navigation with intraoperative images, demonstrating the feasibility of recalibrating navigation with intraoperative MRI.