||The interest towards virtual reality (VR) and virtual environments (VE) is growing all the time. The applications being developed for VE run a wide spectrum, from games to business planning. This thesis concentrates on navigation in virtual architectural environments, movement in worlds that are very similar to our own. Navigation in a virtual world should be practical, intuitive and simple. Unfortunately, it is very often far from that - for some reason the usability issues in VEs have been usually left with little attention. Currently it is easy for a user to get lost and disoriented when traveling in a VE. This situation must change, navigating through virtual environments can no longer be considered a task reserved for the experts only. 3D-worlds and architectural applications for the common user require new, intuitive interface techniques. This thesis addresses issues related to both physical and cognitive aspects of navigation as well as theoretical models that bind them together. In the technology survey of this thesis, the virtual environment technology is presented. Different visual display systems, new input devices and some 3D user interface design aspects are described. The literature survey section discusses the main issues concerning navigation theory. The two parts of navigation, travel and wayfinding, are described in detail. The major challenges are discussed and some solutions and various research results are presented. A major part of the thesis consists of the description of HCNav, a new navigation system developed by the author. The system was constructed for use in the virtual room at Helsinki University of Technology. The purpose of HCNav is to provide a very intuitive and practical navigation interface. Three new experimental input devices, namely custom wand, data glove and speech recognition system, were tested. Another important part of the work is to evaluate the effectiveness of the HCNav system. A usability test was conducted to determine if the use of HCNav was actually improving navigation performance. Twelve subjects participated in a test where HCNav was compared with a traditional navigation software used previously in the virtual room. The experiment setup has been described and the results analyzed. The results are promising and show that the navigation methods adopted in HCNav are clearly better.