OBJECTIVES: The purpose of this study was to investigate the prevalence of alcoholism among inpatients, to identify social and demographic factors associated with this prevalence and to determine its rate of recognition by the medical team. METHODS: The study population consisted of all patients admitted to the emergency room at Hospital São Lucas, Porto Alegre, Brazil, between July and September of 2005. The data were collected in two steps: an interview with the patient and a review of the medical records to investigate the cases of alcoholism recorded by the medical team. The questionnaire consisted of questions concerning social and demographic data, smoking habits and Alcohol Use Disorders Identification Test. RESULTS: We interviewed 248 patients. Twenty-eight (11.3%) were identified as alcoholics. Compared to the patients with a negative Alcohol Use Disorders Identification Test value (less than 8), those with a positive Alcohol Use Disorders Identification Test were more likely to be male, illiterate and smokers. The medical records of 217 (87.5%) patients were reviewed. Only 5 (20.0%) of the 25 patients with a positive Alcohol Use Disorders Identification Test whose medical records were reviewed were identified as alcoholics by the medical team. The diagnosis made by the medical team, compared to Alcohol Use Disorders Identification Test, shows only a 20% sensitivity, 93% specificity and positive and negative predictive values of 29% and 90%, respectively. CONCLUSION: Alcoholism has been underrecognized in patients who are hospitalized, and, as such, this opportunity for possible early intervention is often lost. Key social and demographic factors could provide physicians with risk factors and, when used together with a standardized diagnostic instrument, could significantly improve the rate of identification of alcoholic patients.