Aims: To address the accuracy of quantity-frequency (QF) questions in screening for hazardous or harmful drinking. Methods: Three groups were interviewed: patients presenting to emergency departments for care of an acute injury (n = 1537) or a medical illness (n = 1151), and community controls interviewed by telephone (n = 1112). The first question about alcohol was a single alcohol screening question (SASQ), When was the last time you had more than X drinks in one day?', where X = 4 for women and 5 for men, with any time in the past 3 months considered a positive screen (1 drink = 14 g ethanol). The subsequent alcohol questions were a calendar-based review of recent drinking and the alcohol questions from the diagnostic interview schedule (DIS), which included questions about usual frequency and average quantity. Hazardous drinking was defined as drinking >4 drinks in 1 day or >14 drinks in 1 week for men (women 3 and 7) (Guidelines of the US National Institute on Alcohol Abuse and Alcoholism). Current alcohol use disorders were defined using DSM-IV criteria. The areas under the receiver operating characteristic (ROC) curves in identifying hazardous drinking or current alcohol use disorder were compared. Results: The area under the ROC curves in the three samples combined were 0.81 for SASQ (95% confidence interval (CI) 0.79-0.82), 0.80 for a question about average quantity alone (0.79-0.82) and 0.85 for the product of usual frequency times average quantity (0.84-0.86). The QF product and the question about average quantity performed consistently across the three groups. Conclusions: In clinical settings, one way to put these findings into practice is to screen first with a single question, such as the SASQ, a single question about typical quantity, or a question about the frequency of heavy drinking such as the third item of the alcohol use disorders test (AUDIT).