This natural experiment investigates the introduction and use of a pair of competing video telephone systems in a company over a period of 18 months. Both quantitative, time-series analyses and in-depth interviews demonstrate that employees adopted and used the video system for both utility and normative reasons. Consistent with utility explanations, people in the most communication-intensive jobs were the most likely to use video telephony. Consistent with social influence explanations, people used a particular system more when more people in general were using it and when more people in their work group were using it. There were two conceptually distinct, but empirically entangled. types of social influence. First, use by other people changed the objective benefits and costs associated with using the system, and thus their utility. Second, use by others changed the normative environment surrounding the new technology. Both utility and normative influences were stronger in one’s primary work group. Implementers, users, and researchers should consider both utility and normative factors influencing both the success and failure of new organizational communication systems.