Specific deterrent theory suggests an inverse relation between recidivism and time served, while social bonding theory suggests a direct relation. A review of these two theories suggested a U-shaped function. Data supported the hypothesis that the time served affects post-prison recidivism rates and that the direction of the effect varies by the class of offense. The recidivistic effect of longer prison sentences is complex and is likely to be offender-specific. Thus, a sentence can be either too long or too short for a specific individual. The research represents the first effort to synthesize the two major theoretical models and provides an explanation for the failure of past empirical work to establish a relation between time served and recidivism. Tables, appended model, and 45 references. (Author abstract modified)