Policy discussions center around both the functions served by parole supervision and the effectiveness of the supervision in serving those functions. Community protection and assistance to offenders in their reintegration into the community are generally viewed as the main functions of the supervision. However, evaluations of supervision are hampered by the effects of the selection of offenders, the fact that parolees are released earlier than inmates held to full term, the variations in assistance and control provided different parolees, and the role of surveillance. Some studies have tried to control for the effects of each of these factors. However, the research does not yet provide definitive answers. The limitations of existing knowledge suggest that the most rational policy choice about parole supervision is to defer a decision while undertaking careful research. The existing research indicating that parole supervision is ineffective in reducing recidivism also suggests the need for imposing a deadline for the research. Notes, suggested research design, and 29 references.