3D virtual environments have been successfully used in the computer games industry, product design development and military/industrial training. However, most of the existing systems have a supporting structure closely tight to the application. As a result, a change in the application usually means a change in the 3D VE supporting structure, making it difficult and expensive to develop and/or to extend VEs. The integration of non-linear stories and VR is an interesting approach to building and extending 3D VEs when these are built as interactive stories, which can be changed either completely or partially. This paper presents a description language based on XML that is capable of expressing VEs through interactive non-linear stories. When this language is interpreted, it can favour the extension of VE applications, such as highly dynamic marketing campaigns to 3D virtual shops in the web, customized training courses, educational and entertainment games, etc.