The biannual conferences bring together researchers from a wide variety of fields sharing a common interest in reasoning about rationality and knowledge. the impact of this tradition, going back to 1986, is apparent in many of today's research trends and in the growth of an intellectual community beyond traditional disciplinary boundaries. this volume documents the eleventh conference, held in Brussels, Belgium, in June 2007. it includes contributed papers, 3 invited talks. Like earlier volumes in this series, it gives a window of the state of the art in studies of knowledge and information flow in areas such as probability, linguistic semantics, logics for communication, belief revision, game theory, and interactions between these. should be of value for researchers, teachers, and students alike.