Debate continues on the effectiveness of alternatives to incarceration. Many criminal justice professionals and researchers contend that such alternatives may seriously restrict the criminal justice system's ability to incapacitate active offenders. To assess probation and parole failure rates in Louisiana, data were obtained on burglary and armed robbery offenders included in the 1974- 1986 New Orleans Offender Study. Of 4,160 probation terms and 327 parole terms selected for analysis, it was found that 50 percent of probationers and 46 percent of parolees were rearrested for an index offense during their supervision period. The authors argue, however, that high failure rates on probation and parole do not necessarily imply a significant loss in the incapacitative effects of imprisonment. They suggest that a more appropriate measure of the loss of incapacitative effects is the proportion of all offenses committed by persons on probation or parole. Other studies of alternatives to incarceration are reviewed, and policy implications of the New Orleans findings are discussed. 27 references, 11 footnotes, and 4 tables