California’s voter-initiated Proposition 36 (Prop 36) program is often unfavorably compared with drug courts but little is empirically known about the comparative effectiveness of the two approaches. Using statewide administrative data, analyses were conducted on all Prop 36 and drug court offenders with official records of arrest and drug treatment. Propensity score matching was used to create equivalent groups, enabling comparisons of success at treatment discharge, recidivism over 12 months posttreatment entry, and the magnitude of behavioral changes. Significant behavioral improvements occurred for both Prop 36 and drug court offenders, but although more Prop 36 offenders were successful at discharge, more recidivated over a period of 12 months. Core programmatic differences likely contributed to the differences in outcomes. Policy implications are discussed.