In this study, the authors evaluated a low-cost contingency management (CM) procedure for reducing cocaine use and enhancing group therapy attendance in 77 cocaine-dependent methadone patients. Patients were randomly assigned to 12 weeks of standard treatment or standard treatment with CM, in which patients earned the opportunity to win prizes ranging from $1 to $100 for submitting cocaine-negative samples and attending therapy. Patients in the CM condition submitted more cocaine-negative samples and attended more groups than patients in standard treatment. The best predictor of cocaine abstinence at follow-up was duration of abstinence during treatment. On average, patients in the CM condition earned $117 in prizes. Data from this study suggest that some aspects of reinforcement can be implemented in group therapy in community-based clinics.