HOPE (Hawaii Opportunity Probation With Enforcement) as a pilot project reduced drug use, crime, and incarceration, resulting in a savings to the government of approximately $6,000 per participant per year through reduced incarceration. The program cost about $1,400 per participant per year, over and above the cost of routine probation, with most of the additional expenditure spent on treatment. Just over half of the HOPE probationers never violated the rules of the program by missing a drug test or testing positive for drugs over the course of their first year in the program. HOPE achieved its goals of reductions in drug use, new crime, and incarceration among high-risk probationers and in a randomized controlled trial among general-population probationers. Compared to otherwise similar offenders on routine probation, HOPE probationers were arrested less than half as often. They averaged approximately the same number of days in jail for probation violations, and they spent about one-third as many days in prison on revocations and new convictions. A probationer newly assigned to HOPE faces drug testing that is not only more frequent than encountered on routine probation (six times a month compared to once a month), but also faces random rather than prescheduled testing. Under HOPE, every detected violation leads to a hearing and a sanction. As a result, a new HOPE probationer is more likely to experience a court hearing and jail than an otherwise similar probationer not assigned to HOPE. The deterrent effect is so significant, however, that after the initial month or two, a HOPE probationer requires less effort to supervise than a non-HOPE probationer.