The aim of this study was to examine the effectiveness of low-magnitude behavioral incentives in improving attendance for abstinence-treated patients and sustaining illicit-drug abstinence for methadone-treated patients. Subjects were randomly assigned to either incentive or control conditions, with target behaviors differing for the two patient groups (attendance for abstinence-treated and abstinence for methadone-treated patients). Controls received no incentives, whereas incentive subjects could earn $5/day in vouchers during the first 7 days of an intensive outpatient treatment. Results showed that $5/day did not significantly improve attendance in abstinence-treated patients or impact drug abstinence in methadone-treated patients. The data suggest that low-magnitude voucher incentives enhanced treatment attendance by methadone-treated subjects. Although modest monetary incentives had some utility in improving attendance in methadone-treated patients, more potent interventions are needed to improve attendance and maintain abstinence in this high-risk population.