Plan Recognition in Natural Language Dialogue critically examines plan recognition - the inference of an agent's goals and how he or she intends to achieve them. It describes significant models of plan inference and presents in detail the author's own model, which infers new goals from user utterances and integrates them into the system's model of the user's plan, incrementally expanding and adding detail to its beliefs about what the information seeker wants to do. Carberry then outlines computational strategies for interpreting two kinds of problematic utterances: utterances that violate the pragmatic rules of the system's world model and intersentential elliptical fragments. She also suggests directions for future research.