Background: Morbid obesity is the leading public health crisis in the United States, with bariatric surgery as the only effective and enduring treatment for this disease. a concern has been raised, that, postoperatively, alcohol metabolism might be altered in gastric bypass patients. We hypothesized that alcohol metabolism in the postoperative gastric bypass patient would be altered. Methods: Of 36 subjects, 17 control and 19 postgastric bypass subjects each consumed 5 oz of red wine. They underwent an alcohol breath analysis every 5 minutes. The outcomes recorded included symptoms, initial peak alcohol breath level, and the time for alcohol breath levels to normalize. Results: The gastric bypass group was on average 10 years older and had a greater weight and body mass index than the control group. The average time after gastric bypass was 2 years, with an average body mass index loss of 18 kg/m(2) (51 kg/m(2) before versus 33 kg/m(2) after). The gastric bypass patients had a peak alcohol breath level of 0.08% and the controls had a level of 0.05%. The gastric bypass group needed, on average, 108 minutes to reach an alcohol breath level of 0; the control group reached this level after an average of 72 minutes. Both groups showed a similar postingestion symptom profile. Conclusion: In this study, alcohol metabolism was significantly different between the postgastric bypass and control subjects. Although the gastric bypass patients' had a greater peak alcohol level and a longer time for the alcohol level to reach 0 than the controls, the gastric bypass group did not experience more symptoms than the control group. These findings provide caution regarding alcohol use by gastric bypass patients. (Surg Obes Relat Dis 2007;3:543-548.) (C) 2007 American Society for Metabolic and Bariatric Surgery. All rights reserved.