Introduction: This research set out to determine whether communities of practice can be entirely Internet-based by formally applying Wenger's theoretical framework to Internet collectives. Method: A model of a virtual community of practice was developed which included the constructs Wenger identified in co-located communities of practice: mutual engagement, shared repertoire, joint enterprise, community and learning or identity-acquisition. The model included additional empirical attributes associated with higher community-of-practice potential: professional topic, high interaction-volume, non-conflictual focused discussions and core-periphery structure. A systematic search of the Usenet discussion network detected eleven news groups displaying these attributes and they were formally tested for the presence of the Wenger constructs. Analysis: A quantitative survey of news group participants and a qualitative content analysis of core-member discussions were applied to select news groups to detect the Wenger constructs, conservatively assessed as present only when both methods concurred. Results: Four online collectives, evenly divided between computer and non-computer topics, were assessed as Usenet-based communities of practice because they exhibited the complete set of Wenger constructs. Conclusions: This provides evidence that extra-organizational communities of practice can emerge spontaneously in the social areas of the Internet, just as they emerge in organizational settings and that true communities of practice are not inherently limited to face-to-face interaction. (Contains 6 figures and 13 tables.)