DTAP diverts prison-bound repeat felony offenders to residential drug treatment. The program targets drug-addicted defendants arrested for nonviolent felony offenses who have previously been convicted of one or more nonviolent felonies. For the first 7 years of the program, it operated as a deferred prosecution program in which the adjudicative process was halted or suspended to allow accepted defendants to participate in residential drug treatment for 15 to 24 months. Those who completed the program had their charges dismissed; those who dropped out or were expelled were brought back to court by a special warrant enforcement team and prosecuted on the original charges. Official arrest data were examined for the 263 offenders who were arrested in police undercover operations for drug sales and entered DTAP between December 1990 and December 1992. Of these, 182 successfully completed treatment, and the remaining 81 failed treatment and were subsequently prosecuted and sentenced to prison. Both "completers" and "failures" were detained in jail during the preadmission screening period, which averaged 49.5 days for the entire sample. Recidivism was defined as the first official rearrest that occurred within the 3-year period following treatment completion or prison release. Eighty (30 percent) of the 263 subjects were rearrested during the 3-year follow-up period. Lengths of incarceration and treatment were the main predictors and reflected the hypothesized conceptual constructs of deterrence and rehabilitation. The data show that although all subjects were exposed to both incarceration and residential drug treatment, only treatment decreased the likelihood of recidivism. No evidence of deterrence was found, and there were some indications of the criminogenic influence of incarceration among studied subjects. These findings support current efforts to reform draconian mandatory sentence laws for nonviolent drug offenders. 3 tables and 37 references