The best predictor of future criminal behavior is past criminal behavior. At the same time, the vast majority of people who engage in crime are teenagers and stop offending with age. Explaining these empirical findings has been the main task of life-course criminology, and contributing to an understanding of how and why offenders continue their criminal careers once they have started, and how and why they stop, is also the purpose of this dissertation.To do this, the dissertation studies a number of facets of the criminal career: the importance of childhood risk factors (Paper I), the notions of turning points (Paper II) and intermittency (Paper III), and the connection between masculinities and criminal careers (Paper IV). In contrast to much life-course criminological research, the dissertation mainly relies on qualitative life history interviews, collected as part of The Stockholm Life Course Project.The findings suggest a need for increased sensitivity to offenders’ lives, and their complexity. Whereas continuity and change can be understood within a frame of age-graded social control, this perspective needs to be extended and developed further, in mainly three ways. First, the concept and phenomenon of human agency needs closer study. Second, lived experiences of various forms of social stratification (e.g. gender, ethnicity, and so on) must be integrated into understandings of continuity and change in crime, seeing as phenomena such as social control may be contingent on these in important ways. Third, this dissertation highlights the need to go beyond the transition to adulthood and explore the later stages of criminal careers.In closing, the dissertation suggests that we move toward a focus on the contingencies of criminal careers and the factors, events, and processes that help shape them. If we understand those contingencies in more detail, possible implications for policy and practice also emerge.