Recognition of incipient change in the status of English as an international language has yielded a small but growing area of research addressing nonnative speaker to nonnative speaker (NNS-NNS) interaction. Issues concerning intelligibility are a key focus of this investigation, particularly as native speaker models have limited relevance to these new contexts of use. This review highlights current research from diverse areas of applied linguistics that have addressed aspects of intelligibility in both experimental and real-world settings. Current findings suggest that the processes by which understanding is achieved in English as a lingua franca (ELF) interaction are qualitatively different from those observed in native speaker (NS)–based interaction, and that this has implications for a number of research and practice areas. Following a definition of terms, the chapter surveys current research and considers its influence on current trends in English language teaching. Possible directions for further research are also considered.