Purposes: A paucity of data exists on the prevalence and predictors of discharging injured patients against medical advice from emergency departments. The aim of this study is to investigate the association between acute alcohol use and being discharged against medical advice. Methods: We performed a prospective, observational study of injured patients enrolled into the Korean Centers for Disease and Prevention injury surveillance program in 7 tertiary, academic, and teaching hospitals from June 1, 2008, to November 31, 2011. Injured patients were assigned to 1 of 3 groups: discharged against medical advice, regular discharge, and transferred or admitted. Multivariable logistic regression models were used to analyze the association between acute alcohol use and being discharged against medical advice. Results: A total of 125,327 patients were enrolled, and 3473 (2.8%) were discharged against medical advice. The proportion of acute alcohol use was significantly higher among the patients who were discharged against medical advice (40.1%) than the regular discharged (16.6%) or transferred/admitted (15.5%) patients. In a regression model, acute alcohol use increased the risk of being discharged against medical advice (adjusted odds ratio, 1.86; 95% confidence interval, 1.70-2.03). In addition, we identified the interaction between acute alcohol use and intention of injury. Acute alcohol use had a significant association with the discharge against medical advice with the unintentional injury (adjusted odds ratio, 2.56; 95% confidence interval, 2.30-2.84). Conclusion: Patients with acute alcohol use before sustaining an injury are at increased risk of being discharged against medical advice from the emergency departments.