The new recreational marijuana markets are contributing to morbidity and mortality due to marijuana- and polysubstance-impaired driving and other harms by selling a social intoxicant (i.e., marijuana) to already intoxicated customers. Impairment increases when marijuana is combined with alcohol, making driving particularly risky and also contributing to other injuries and violence. In recreational marijuana markets, deterrence efforts to reduce impaired driving directed at drivers face challenges due to dispute over THC levels in per se laws and lack of valid field sobriety tests. An alternative prevention approach is to decrease access to marijuana by alcohol-impaired customers. The goal of this research is to test the effectiveness of a policy and training (PT) intervention in the state-licensed recreational marijuana market in Oregon, where state law bans sales to obviously-intoxicated customers. It combines policy efforts by state regulators to increase deterrence of Oregon's law and motivate store management to comply and training of store personnel in skills to recognize intoxication and refuse sales, using a responsible marijuana vendor online training developed by the research team. The specific aims of the project are to: 1) conduct pseudo-intoxicated patron (PiP) assessments at state-licensed recreational marijuana stores (n=213) in the greater Portland metropolitan area (i.e., Clackamas, Multnomah, and Washington Counties) in Year 1; 2) implement a PT intervention in Year 2 designed to increase compliance with Oregon law prohibiting sale of recreational marijuana products to obviously-intoxicated customers with a subsample of stores (n=68), assigned at random, that intends to a) make owners/managers of recreational marijuana stores aware of Oregon's law prohibiting sales of marijuana to obviously-intoxicated customers, b) increase their risk perception and motivation to comply with this law, and c) train store personnel in skills needed to recognize signs of intoxication in customers and refuse sales; 3) compare PT intervention stores to usual and customary policy and training (UC-PT) stores (n=145) in a randomized controlled trial by posttesting state-licensed recreational marijuana stores in greater Portland with PiP assessments for refusal of sales in Year 3; and 4) estimate impact of the PT intervention on refusal to PiPs by implementing the PT intervention with the remaining stores in Portland in Year 3 in a partial cross-over design and assessing state-licensed stores in greater Portland with the PiP protocol in Year 4 and in Year 5. The research is innovative and high impact by testing one of the first interventions to prevent recreational marijuana sales to obviously-intoxicated customers in one of the first states to ban such sales to reduce the risk of poly-substance impaired driving and other harms. The design allows for reproducibility by using a partial cross-over to enhance power with both between- and within-group comparisons. The PT intervention can be a model intervention to improve compliance with regulations on recreational marijuana sales in other states that have legalized recreational marijuana, now numbering 17 U.S. states, or that are considering legalization.