BACKGROUND: Brief intervention with problem drinkers have been shown to be effective, but physicians often do not ask about alcohol use because of time constraints and lack of knowledge. If a sin gle question can be used to screening for problem drinker effectively, primary care physicians could detect problem drinker earlier and reduce future complication and morbidity. The purpose of this study was to evaluate the usefulness of single question. METHODS: One family medicine's resident interviewed 163 patients who visited Dongdaemun Hospital's Health care management center of Ewha Woman's university from January 27th 1999 to February 26th 1999, and the patients answered the written forms of questionnares. This written forms contained the followings: (1) age, sex, education, income level, occupation, smoking, drunken driving, (2) "On any single occasion during the past 3 months have you had more than a bottle of Soju or three bottles of beer or five glasses of whisky?" (3) CAGE, NAST test. Quantity of alcohol was determined by the calendar based review in the past 4 weeks. At risk drinker defined as drinking more than 56 g on one occasion, or more than 196 g of pure alcohol during a week for men ; more than 42 g on one occasion, or more than 98 g of pure alcohol during a week for women. Also alcohol use disorder was defined by the DSM IV criteria and problem drinker was defined as either at risk drinker or a alcohol use disorder. RESULTS: The single question had a positive predictive value of 82.2%, and negative predictive value of 95.5% with a sensitivity of 93.8% and a specificity of 86.9% for problem drinkers. CONCLUSION: A single question about alcohol use would be a effective tool for detecting problem drinker.