The ELF in TIGs (English as a lingua franca in Transient International Groups) project has the aim of establishing a comprehensive conceptual, methodological and descriptive framework for the study of communication in transient lingua franca contexts, i.e. situations that are too short-lived, fleeting or unstable to be considered communities of practice. It is concerned with the systematic empirical description of how communication evolves in interaction in different ELF contexts and in different group constellations across time. Overarching questions that drive research in the project include: Under which contextual circumstances do multilingual speakers in different TIGs engage in which linguistic practices to what extent? Which linguistic practices and salient sociolinguistic or pragmatic phenomena can be observed during different phases of group formation, interaction and negotiation in different (E)LF contexts?