Viewpoint tethering, as a way of integrating information from both egocentric and exocentric frames of reference, has been proposed as a means of supporting efficient navigation in virtual environments. In this paper, we report our latest findings on the effects of tether length on navigational performance. Twelve volunteers participated in an experiment in which they were instructed to control an aircraft-shaped cursor flying through a set of virtual tunnels and to answer questions about the environment. Experimental results showed that: (1) subjects' global awareness performance improved with an increase of tether length; and (2) neither the short tether nor the long tether supported the best local guidance performance. Rather, the best performance was observed for an intermediate length tethered display. The existence of an optimal value for this parameter provides useful guidelines for the design of navigational system interfaces.