Abstract. Implementation of new computer-mediated communication (CMC) systems in organizations is a complex socio-technical endeavour, involving the mutual adaptation of technology and organization over time. Drawing on the analytic concept of sensemaking, this paper provides a theoretical perspective that deepens our understanding of how organizations appropriate new electronic communication media. The paper analyzes how a group of mediators in a large, multinational company adapted a new web-based CMC technology (a virtual workspace) to the local organizational context (and vice versa) by modifying features of the technology, providing ongoing support for users, and promoting appropriate conventions of use. We found that these mediators exerted considerable influence on how the technology was established and used in the organization. The mediators were not neutral facilitators of a well-defined technology that presented itself to them as given and fixed. On the contrary, the new technology was from the onset highly equivocal and open-ended, and the mediators were actively involved in creating the technology-in-practice—by making sense of it, defining it, and regulating its use. Implications for further research and for practice are considered