T his paper is about how developers will know whether intelligent virtual environments (IVEs) are appropriate for the tasks set to them. T here are several important research questions that need to be answered before they can even begin to build IVEs for some of the more promising applications, such as entertainment, education, collaboration on research and development, military, and other training.T he main technical point is that every aspect of any IVE involves models, and the modeling needs to be addressed very directly and explicitly.T his paper is more for the developers of such systems and the potential customers, than for the users. More is written about what is important to consider as one contemplates, for example, a difficult collaborative task, than about what it will be like to live in these IVEs.T he authors believe that IVEs must be expanded to become virtual worlds (VW s), and that the modeling sophistication required for any of the serious applications described above is much more than is currently available in the VW s seen, even the ones with good graphics.Finally, the connection between Virtual Reality and CyberSpace is made, and the authors explain their expectations will be explained for the future of CyberSpace.