Computer-assisted surgery (CAS) originated in neurosurgery-stereotaxis surgery, development of computing technique and imaging methods. In enables a peroperation control of the device position in the operation field and the direction of operation proceduře. At the present time the ORL branch employs this technique in connection with endoscopic endonasal surgery and cranial base surgery. Systems of electromagnetic and optical navigation are ušed. CAS offers the surgeon a great deal of peroperation information. However, it also includes some obstacles, which ensue from the possibility of deteriorated navigation in the course of operation or the fact that the localization is compared on the basis of information obtained before the operation and actual situation during the operation, indicating that the co-registration of orientation points must be doně immediately before the operation. The extent of agreement constitutes the measure of navigation precision. CAS is aimed at selected operations. Due to the time and economic requirements it is not suitable for all kinds of operations and the authors estimate it to be suitable in 10% of all endonasal endoscopic operations. CAS is not meant for an inexperienced surgeon to overcome the limite of his/her surgical possibilities, while it serveš to experience surgeons to make complicated interven-tions in the easier and safer way. The communication is based on experience with CAS performed using three devices of different producers since 1999. The authors performed the operation with the use of electromagnetic device Insta Track of VTI company, the optical systems Treon and Tria produced by Medtronic, Inc. and the apparatus vector Visition made by BrianLab. For the functional endoscopic surgery the electromagnetic systém proved to be most flexible for a good precision of navigation. It has got its limitations too, though. At the present time authors operáte on using the Vector Vision device, which they share with the Neurosurgery Clinic, thereby making a maximum efficiency in the application of the apparatus possible. Presumably, CAS should further decrease invasiveness of certain interventions, but apparently does not represent a finál solution in the problém of the surgeon orientation during the operation. It may be expected that the aim is a navigation systém working with in line data in the course of operation for the saké of visualization as well as for localization.

        Key words: computer-assisted rhinosurgery, technical systems, navigation precision, indicati-ons.