After reviewing the literature on research and practice related to reintegration theory, the chapter notes an apparent void in this field of research. Researchers have typically asked "what works?" but rarely ask "how" or "why" an ex-offender achieves a successful reintegration. The editors intend that the essays in this book will reveal a largely untapped resource of criminological theory and research that already exists that holds promise for the development of theories for reintegration practice, i.e., the literature that focuses on "desistance" from crime. The study of crime desistance emerged from the criminal-career literature in the 1980's and 1990's (e.g., Farrington, 1986; Paternoster, 1989; Moffitt, 1993; Sampson and Laub, 1993; Sommers et al., 1994; Graham and Bowling, 1995; Shover, 1996; and Warr, 1998). Although still relatively new, the study of crime desistance has in recent years come of age as a field of scholarly research. As a collection the essays of this book argue that criminal justice policies meant to help ex-offenders reintegrate into society, reform, or rehabilitate are best understood when situated within the larger context of crime desistance and the known correlates of this process. A section of this chapter on the definition of "desistance" distinguishes at least two phases in the desistance process: primary and secondary desistance. Primary desistance refers to any lull or crime-free gap in the course of a criminal career. Because there are a number of such pauses in the course of a criminal career, primary desistance is not be a matter of central theoretical interest. The focus of desistance research is rather on secondary desistance, which is the movement from the behavior of nonoffending to the assumption of the role or identity of a "changed person." In secondary desistance, crime not only stops, but existing roles become disrupted and a reorganization based upon a new role or roles occurs. This chapter concludes with a summary of the layout of the book. 75 references