The Washington State Institute for Public Policy (Institute) was directed by the Legislature to evaluate the impacts of DOSA. DOSA was originally enacted in 1995 as a sentencing alternative. When ordered by a court, a felony offender’s sentence time is reduced in exchange for completing chemical dependency treatment. Prior to 2005 legislation, DOSA was restricted to a “prison-based” treatment alternative. The 2005 changes created a “community-based” DOSA for offenders with non-prison sentences. Because only 30 offenders have received this community alternative to date, further implementation is necessary before an evaluation of the community-based DOSA can be completed. This report updates our 2005 study of the original “prison-based” DOSA, extending the follow-up from 24 to 36-months. In our earlier report, we found that recidivism rates were lower for drug offenders receiving DOSA, but not for property offenders. With a 36-month follow-up, our findings did not change. That is, prison-based DOSA significantly lowers recidivism rates for drug offenders, but has no statistically significant effect on recidivism rates of property offenders.