This book explores how speakers of Japanese organize their messages into coherent units as they jointly and interactively construct conversational discourse. Specifically, it investigates the syntactic, informational, and functional structures of intonation units (IUs) as basic units of discourse production and information flow in spoken communication. It addresses various research topics: clause vs. phrase centrality, relationship between IUs and clauses, functions of independent NPs, preferred argument/clause structure and transitivity, interrelationship among functional components, and the role of new and interactional information in the shaping of IU syntax. Overall, it tries to elucidate not only the preferred IU structures that are typical of the way Japanese speakers talk in connected discourse, but also possible relationships between the structures and their implications. Besides three main chapters discussing the results of quantitative and qualitative analyses, it also includes an introductory chapter comprehensively covering key issues in research on information flow in spoken discourse in general. Thus the book will be useful to all students and researchers of functional linguistics and discourse analysis.