Referential communication is the term given to communicative acts, generally spoken, in which some kind of information is exchanged between one speaker and another. This information exchange is typically dependent on successful acts of reference, whereby entities (human and non-human) are identified (by naming or describing), are located or moved relative to other entities (by giving instructions or directions), or are followed through sequences of locations and events (by recounting an incident or a narrative). These "activities" are examples of events that are more typically described as "tasks" in the area of second language studies. These might be real world tasks encountered in everyday experience or pedagogical tasks specifically designed for second language classroom use. This volume comprehensively documents and describes the growth of task-based research in language acquisition. In an accessible fashion, it presents the origins, principles and key distinctions of referential communication research in first and second language studies, complete with analyses and illustrations of different types of materials. The author also describes and evaluates different choices for using or modifying these materials, provides analytic frameworks for focusing on various aspects of the data elicited by these tasks, and includes an appendix showing original task materials.