This tutorial focused on the application ofnew visualization techniques to the practical problems confronting the neurosurgeon. In particular, the challenging issues associated with presurgical planning and with intra-operative navigation were presented in a tutorial format. The course began with a discussion of algorithms and hardware for intra-operative registration. Traditional frame-based stereotactic techniques were introduced, then several classes of non-invasive registration techniques, including fiducial based algorithms, surface and contour matching algorithms and video mixing approaches were described and compared. The "surgeon-computer interface" was discussed, including issues associated with time constraints, sterility problems, electrical safety, and software validation. Videotaped surgical procedures demonstrating these concepts were shown. The tutorial concluded with a review of various technologies for intraoperative registration and navigation. Mechanical, visible and infra-red camera systems, and ultrasonic techniques were compared. Attendees had the opportunity to gain hands-on experience with several intra-operative wands and with a prototype heads-up-display guidance system.