Under both conditions, prison produced slight increases in recidivism. Also, there was some evidence that lower risk offenders were more negatively affected by the prison experience. Based on the study findings, the authors conclude that offenders should not be sentenced to Canadian prisons under the expectation that this will reduce their criminal behavior after release. Also, if prison increases offender recidivism by even small amounts, then the costs accruing from the excessive use of prison could be enormous; for example, even percentage changes of approximately 5 percent have resulted in significant cost implications in medicine and other areas of human services. It is estimated that the criminal career of just one high-risk offender costs approximately $1,000,000. Arguably, increases in recidivism of even a fractional amount are not fiscally responsible. In order to determine who is being adversely affected by prison, it is incumbent on prison officials to implement repeated, comprehensive assessments of offenders' attitudes, values, and behavior while incarcerated. Given the findings of this study, the primary justification of prison should be to incapacitate offenders, particularly those who are chronic and dangerous offenders, for reasonable periods and to exact retribution. 22 notes, 2 tables, and 100 references