Where sexual offending is considered at all in developmental and life-course criminology (DLC) theories, it is generally understood to occupy a position at more serious end of a continuum of irresponsible, socially deviant, or unlawful behavior. Thus DLC theories explicitly or implicitly assume that the same concepts and principles that apply to all other forms of offending apply equally to sexual offending. This chapter presents an integrated theory of sexual offending that incorporates ideas from DLC approaches. It briefly addresses each of the 10 points listed by David Farrington as the key empirically confirmed developmental dimensions of offending and antisocial behavior. The chapter's aim is to present an integrated theory of sexual offending that considers the contribution of individual, ecological, and situational factors. The theory proposed here is a new iteration of a model originally proposed by Marshall and Barbaree and later revised and extended by Smallbone, Marshall, and Wortley.