The sample consisted of 982 inmates incarcerated in Vermont State correctional facilities who had at least 30 days to serve. The model included person variables, environmental or situation variables, and prison-environmental interaction variables for use in studying the interactions between individuals and their environments and to predict offender behaviors such as escape, misconduct, and violence. The model was designed to enhance the predictive validity of the National Institute of Corrections' classification system being used in Vermont prisons. Included are scores from the National Institute of Corrections' custody classification and reclassification instruments, scores from a needs assessment, sentencing information, and characteristics of the prison in which the inmate is housed. (Author abstract modified)