310 alcohol abusing or dependent patients beginning intensive outpatient day treatment at community-based clinics will be randomly assigned to one of four conditions: (a) standard treatment as usual (ST) at the clinic without contingency management (CM); (b) standard treatment with contingency management for 12 weeks with a 0.5 probability of winning prizes for each negative sample submitted; (c) standard treatment with contingency management for 24 weeks with a 0.34 probability of winning prizes for each negative sample submitted; or (d) standard treatment with contingency management for 24 weeks with a 0.5 probability of winning prizes for each negative sample submitted. We expect that contingency management will decrease alcohol use to a greater extent than non-contingency management treatment, and that availability of contingency management for 24 weeks may result in longer term benefits than 12 week exposure to contingency management. This study will be the first to evaluate the effects of probability of winning prizes on response to contingency management.