Mentalization is the capacity to perceive and interpret behavior in terms of intentional mental states, to imagine what others are thinking and feeling, and is a concept that has taken the psychological and psychoanalytic worlds by storm. This collection of papers, carefully edited by Fredric Busch, clarifies its import as an essential perspective for understanding the human psyche and interpersonal relationships. The book is divided into theoretical, research and clinical papers, reflecting how the investigators thoughtfully and purposefully pursued each of these goals. Those involved in identifying mentalization have also made consistent efforts to measure and research the concept. Thus, in addition to expanding the theoretical bases and implications of mentalization and identifying clinically useful applications, the authors describe research that scientifically grounds the concept. Mentalization addresses and expands upon a number of implications of mentalization. These include: What are the broader implications for mentalization with regard to social and evolutionary development? How does mentalization interdigitate with other psychoanalytic models? How is mentalization systematically assessed? What clinical correlates have been found? How do we understand variations in the capacity for mentalization, even within a given individual? What are the applications of mentalization in the clinical arena, including specific disorders? Readers of this volume will find their clinical work to be more productive and their view of the human psyche broadened.