Proponents of the shock probation program maintain that a short period of incarceration for youthful offenders (90 to 130 days) followed by probation will 'shock' them into law-abiding behavior. The proposition that youthful first offenders would be most likely to succeed when released on shock probation was tested through predictive attribute analysis of outcome variables obtained from the Ohio Probation Department files on a sample of 1,081 shock probationers released in 1975. Results of the analysis revealed that prior record was the best predictor of failure (reincarceration over a 2-year period). Type of offense had an impact among the first offenders, with property offenders failing at a rate more than twice that of offenders who committed crimes against the person. Also, nonhigh school graduates failed at a rate nearly four times that of their high school graduate counterparts among first offenders who committed crimes against the person. Age and the presence of dependents were variables that caused the highest rates of failure among offenders with a prior record. Type of supervision made a difference with nonwhite first offenders, in that individuals under county supervision failed at a rate more than twice that of their State-supervised counterparts. It is concluded that study findings validate the guidelines of Ohio's shock probation program; namely, that shock probation is most effective when applied to youthful first offenders. However, it is urged that data findings not be applied mechanically without consideration given to individual circumstances of prior offenders. Two text data tables and 21 references are provided.