Much of the prior research on probation outcome measured outcome as success or failure while under supervision or during the postprobation period. Failure in a majority of those cases was measured by reconviction, revocation, or absconding; success was measured by the completion of the probation term without the occurrence of those events. In the literature reviewed for this study, there was little uniformity in the definition of failure. None of the studies indicated use of a control group for comparison. Studies of postprobation outcome used different follow-up periods, from as short as 6 months to as long as 7 years. Study populations were different, including felons, misdemeanants, or a combination; Federal probationers; and probationers supervised by state probation agencies. More research is needed into issues including whether probation expands the area of social control, what probation can and cannot do, and for whom probation works best. Tables, references