Despite its potential benefits, the effectiveness of CMC when used to support learning in higher education is very variable, making it important to identify those factors which best predict successful implementations. A review of the literature from the past few years, presented in the first half of this paper, suggests that, consistent with Activity Theory (Leont'ev, 1978), the critical factors are those which provide a context and rationale for online communication by helping users to establish a shared purpose. However, generating empirical support for this hypothesis presents two kinds of methodological problem: specifying the methods and measures necessary to discern the existence and impact of shared purpose; and dealing with the difficulties of making controlled comparisons in this area. The second half of the paper illustrates, via an implementation case study, something of how these methodological problems might be resolved, and presents evidence in favour of the central importance of shared purpose
