We describe the development of the CaveUT system, which is a software supporting immersive virtual reality installations based on the Unreal Tournament game engine. CaveUT implements several high-end VR features such as real-time stereoscopy with head and hand tracking. We demonstrate the use of CaveUT in the SAS Cube™, a PC-based CAVE™-like immersive fourscreen display. One of the main advantages of the system is to support full immersive VR while retaining the advanced features of game engines in terms of interaction and inclusion of behavioural (or AI) systems. We illustrate the use of CaveUT on two installations: an artistic VR installation and an immersive interactive storytelling system. Categories and Subject Descriptors H5.1 [Multimedia Information Systems] Artificial, Augmented and Virtual Reality - Virtual Reality for Art and Entertainment. General Terms Design and Experimentation. Keywords Game engine, Immersive Displays, Digital Arts, and Intelligent Virtual Environmen...