The vision of integrating magnetic resonance (MR) technology into the neurosurgical operating room is relatively new. The primary goal is the fusion of direct vision and image-based information. The ideal intraoperative magnetic resonance imaging (iMRI) system needs to incorporate the features and characteristics of both the operating room and a diagnostic MR suite (1). Currently the best imaging modality for examining the central nervous system and defining pathologic changes is magnetic resonance imaging (MRI). The main reason is the ability of MRI to delineate soft tissue structures in a multiplanar, radiation-free fashion. MR also is able to characterize both anatomical and functional properties of normal and diseased tissue. The neuroradiologist and neurosurgeon use this information to define the intracranial target and preoperatively plan the neurosurgical corridor to the lesion. Intraoperative MRI updates the preoperative diagnostic studies, refines the surgical approach, confirms accomplishment of surgical objectives, and excludes acute surgical complications. By updating spatial coordinates, injury to normal tissue is minimized. Intraoperative use of MRI provides information not available from direct visual examination of the surgical field. The neurosurgeon’s view of surface structures within the operative area is complemented by volumetric MR images showing subcortical structures. Based on MRI data, three-dimensional (3D) models of the relevant anatomy and pathology can be generated and presented to the surgeon along with the original MRI (2,3) (Fig. 1). These may include the pathologic target, vessels, white matter tracts, basal ganglia and other nuclei, cisterns, and ventricles. Cross-referencing of the surgical view and volumetric images is accomplished by intraoperative navigational guidance systems. Before the introduction of iMRI, frameless stereotaxy relied on preoperatively acquired, archived images. Frequent intraoperative image updates (not necessarily real time), however, allow adjustment of the image-based models to the deformation and shift of brain structures with surgery (4– 6). This has resulted in a fundamental change in operating techniques with closer integration of image data into the surgical procedure. Neurosurgeons have embraced the benefits of intraoperative guidance with greater alacrity than their colleagues in other surgical specialties. This relatively rapid success is due to the fact that the concepts of imageguided surgery and its benefits already are acknowledged in neurosurgery. The introduction of near real-time image updates has improved localization and targeting, as well as confirmation of surgical objectives. This early success of MRI-guided therapy in the field of neurosurgery needs to be extended and exploited.