This thesis is concerned with the design of Virtual Environments (YEs) - in particular with the tools and techniques used to describe interesting and useful environments. This concern is not only with respect to the appearance of objects in the VE but also with their behaviours and their reactions to actions of the participants. The main research hypothesis is that there are several advantages to constructing these interactions and behaviours whilst remaining immersed within the VE which they describe. These advantages include the fact that editing is done interactively with immediate effect and without having to resort to the usual edit-compile-test cycle. This means that the participant doesn't have to leave the VE and lose their sense of presence within it, and editing tasks can take advantage of the enhanced spatial cognition and naturalistic interaction metaphors a VE provides. To this end a data flow dialogue architecture with an immersive virtual environment presentation system was designed and built. The data flow consists of streams of data that originate at sensors that register the body state of the participant, flowing through filters that modify the streams and affect the yE. The requirements for such a system and the filters it should contain are derived from two pieces of work on interaction metaphors, one based on a desktop system using a novel input device and the second a navigation technique for an immersive system. The analysis of these metaphors highlighted particular tasks that such a virtual environment dialogue architecture (VEDA) system might be used to solve, and illustrate the scope of interactions that should be accommodated. Initial evaluation of the VEDA system is provided by moderately sized demonstration environments and tools constructed by the author. Further evaluation is provided by an in-depth study where three novice VE designers were invited to construct VEs with the VEDA system. This highlighted the flexibility that the VEDA approach provides and the utility of the immersive presentation over traditional techniques in that it allows the participant to use more natural and expressive techniques in the construction process. In other words the evaluation shows how the immersive facilities of VEs can be exploited in the process of constructing further VEs.