This paper presents a model for assessing the performance of virtual teams. The model has 19 outcomes, 60 factors and 23processes. The outcomes serve as indicators of team performance. The factors and processes interact to create the performance ofthe team. Investigating the outcomes, and then the factors and processes facilitates understanding the performance of a virtualteam. An initial model was derived from extensive literature review. It has been used, and extended, in three case studies. Whilenot an empirically proven model it has proved practical for undertaking case studies and particularly for the purposes of crosscasecomparison. It appears to be the most comprehensive model for researching virtual teams currently available.