Collaborations in organizations thrive on communication that is informal because informal communication is frequent, interactive, and expressive. Informal communication is crucial for the coordination of work, learning an organization's culture, the perpetuation of the social relations that underlie collaboration, and, in general, any situation that requires communication to resolve ambiguity. Informal communication is traditionally mediated by physical proximity, but physical proximity cannot mediate in geographically distributed organizations. The research described here evaluates the adequacy of a version of a desktop video/audio conferencing system for supporting informal communication in a research and development laboratory. The evaluation took place during a trial in which the system was used by summer employees and their supervisor-mentors.While the system was used frequently, the most common uses and users' assessments suggest that it was used more like a telephone or electronic mail than like physically mediated face-to-face communication. However, some features of its use transcended traditional media and allowed users to gain awareness of their work environment. The paper concludes with a discussion of requirements for successful technology to support informal communication.