[Computer-aided 3D-navigation systems. Survey and location determination]

3D-navigation systems have only recently been introduced into the surgical field. Since then they have gained increasing importance not only in ENT surgery but also in neurosurgery, orthopedic surgery, maxillo-facial surgery, radiology and radiotherapy. Following a brief historical introduction this article reviews existing navigation technologies, in terms of indication, practicability, accuracy, forensic and financial aspects. The selection of the navigation system is strongly influenced by the planned procedure (endoscopic, microscopic, open approach). According to our experience most of these systems provide useful support intraoperatively. The clinical application accuracy regularly lies in the range of 1-2 mm.