The paper systematically explores the social dimension of external interruptions of human activities. Interruptions and interruption handling are key issues in human-computer interaction (HCI) and computer-supported cooperative work (CSCW) research. However, existing research has almost exclusively dealt with effects of interruptions on individual tasks. In this paper we call for expanding the scope of analysis by including the effect of interruptions on the social context. We identify four facets of the social "ripple effect" of interruptions: location, communication, collaboration, and interpersonal relation. We discuss the advantages of extending the notion of interruptions and its implications for future research. Categories and Subject Descriptors H.5.3 [Information Presentation and Interfaces]: Group and Organization Interfaces