IMPORTANCE Excessive alcohol use is one of the most common causes of premature mortality in the United States. From 2006 to 2010, an estimated 88 000 alcohol-attributable deaths occurred annually in the United States, caused by both acute conditions (eg, injuries from motor vehicle collisions) and chronic conditions (eg, alcoholic liver disease). Alcohol use during pregnancy is also one of the major preventable causes of birth defects and developmental disabilities. OBJECTIVE To update the US Preventive Services Task Force (USPSTF) 2013 recommendation on screening for unhealthy alcohol use in primary care settings. EVIDENCE REVIEW The USPSTF commissioned a review of the evidence on the effectiveness of screening to reduce unhealthy alcohol use (defined as a spectrum of behaviors, from risky drinking to alcohol use disorder, that result in increased risk for health consequences) morbidity, mortality, or risky behaviors and to improve health, social, or legal outcomes; the accuracy of various screening approaches; the effectiveness of counseling interventions to reduce unhealthy alcohol use, morbidity, mortality, or risky behaviors and to improve health, social, or legal outcomes; and the harms of screening and behavioral counseling interventions. FINDINGS The net benefit of screening and brief behavioral counseling interventions for unhealthy alcohol use in adults, including pregnant women, is moderate. The evidence is insufficient to assess the balance of benefits and harms of screening and brief behavioral counseling interventions for unhealthy alcohol use in adolescents. CONCLUSIONS AND RECOMMENDATION The USPSTF recommends screening for unhealthy alcohol use in primary care settings in adults 18 years or older, including pregnant women, and providing persons engaged in risky or hazardous drinking with brief behavioral counseling interventions to reduce unhealthy alcohol use. (B recommendation) The USPSTF concludes that the current evidence is insufficient to assess the balance of benefits and harms of screening and brief behavioral counseling interventions for alcohol use in primary care settings in adolescents aged 12 to 17 years. (I statement)