Previous studies have explained the transition from criminal propensity in youth to criminal behavior in adulthood with hypotheses of enduring criminal propensity, unique social causation, and cumulative social disadvantage. In this article we develop an additional hypothesis derived from the life-course concept of interdependence: The effects of social ties on crime vary as a function of individuals' propsensity for crime. We tested these four hypotheses with data from the Dunedin Study. In support of life-course interdependence, prosocial ties, such as education, employment, family ties, and partnerships, deterred crime, and antisocial ties, such as delinquent peers, promoted crime, most strongly among low self-control individuals. Our findings bear implications for theories and policies of crime.