Clinical guidelines recommend addressing adolescent alcohol use in primary care; the 5 As (Ask, Advise, Assess, Assist, Arrange) may be a useful model for intervention. We audio-recorded 540 visits with 49 physicians and adolescents, compared alcohol disclosure rates in the encounter with those in a survey, and analyzed conversations for use of the 5 As and their relation to adolescent reports of drinking 3 months after the encounter. When physicians asked clear, nonleading questions, drinkers were more likely to disclose alcohol use (P = .004). In 64% of visits in which alcohol was discussed, physicians used one or more of the 5 As, most frequently "Ask." No physician used all 5 As. Among drinkers, there was no association between physicians' partial use of the 5 As and adolescent alcohol consumption at 3 months. Physicians can learn more effective ways to "Ask" about alcohol use to increase disclosure of drinking and to be more comprehensive in their counseling.