We introduce a method for predicting the network traffic that will be generated by Collaborative Virtual Environment applications with varying numbers of participants. Statistical analysis of event logs from user trials results in a user behaviour model. Controlled traffic measurements combined with an analysis of the application architecture and network topology results in a system behaviour model. These two models are combined to produce a network traffic model. We describe the application of this method to a business game application that has been developed as part of the COVEN project. Finally, we make some general observations concerning the network traffic generated by CVEs including its bursty nature and the potential use of techniques such as multicasting and statistical multiplexing to reduce network load.