Navigation is one of the most common and universal interaction tasks performed with 3D user interfaces, and different travel techniques can have a strong influence on a user's exploration and overall experience of a virtual environment. Real walking is considered to be the most natural technique since it mirrors the way most people move about in the real world. However, due to practical limitations, virtual travel techniques are more commonly used in virtual reality applications. Although recent advantages in tracking technology have made real walking viable for many applications, the benefits and drawbacks of this technique are not well understood, particularly in relation to human cognition.To investigate the cognitive effects of real walking, a series of three user studies were conducted to experimentally evaluate common travel techniques for immersive virtual environments using head-mounted displays. In general, these studies have identified criteria where real walking provides notable benefits, and conversely they have demonstrated that virtual travel techniques can be used as less expensive substitutes under the right conditions. Based on the results of these studies, guidelines were developed to outline the advantages and disadvantages of these techniques with respect to the particular goals of the virtual environment. Developers of future virtual reality applications may use these guidelines to weigh the benefits of using a certain travel technique against potential drawbacks or practical limitations.