A sample of inmates serving custodial sentences at an English prison was randomly selected to include 10 percent of the inmate population. The risk assessment procedure was conducted with 65 inmates. Presentence information was obtained from police reports, trial summaries, social inquiry reports, psychiatric reports, and, when available, documents pertaining to previous convictions and earlier prison behavior. Psychologists identified principal risk behaviors associated with an offense. In addition, prison officers who had personal knowledge of the inmates completed a behavioral checklist. The results suggest that it is possible to accurately predict offense-related behavior in the prison environment based on an objective, behavioral analysis of the offense. A crucial aspect of the risk assessment procedure used in the current study is the need to record only well-documented behavioral aspects of an offense. As the inmate proceeds through his or her sentence, the level of risk can be assessed periodically by reviewing the occurrence of predicted behaviors. The level of information available about an inmate is important in evaluating predicted behavior. 46 references, 3 tables, and 3 figures