BACKGROUND Alcohol use is a leading cause of mortality and morbidity internationally, and is ranked by the World Health Organization (WHO) as one of the top five risk factors for disease burden. Without treatment, approximately 16% of hazardous or harmful alcohol users will progress to more dependent patterns of alcohol consumption. This review covers interventions in hazardous or harmful, but not dependent, alcohol users. METHODS We conducted a systematic review and aimed to answer the following clinical questions: What are the effects of interventions in hazardous or harmful drinkers in the primary-care setting? What are the effects of interventions in hazardous or harmful drinkers in the emergency-department setting? We searched: Medline, Embase, The Cochrane Library, and other important databases up to February 2009 (Clinical Evidence reviews are updated periodically; please check our website for the most up-to-date version of this review). We included harms alerts from relevant organisations such as the US Food and Drug Administration (FDA) and the UK Medicines and Healthcare products Regulatory Agency (MHRA). RESULTS We found 18 systematic reviews, RCTs, or observational studies that met our inclusion criteria. We performed a GRADE evaluation of the quality of evidence for interventions. CONCLUSIONS In this systematic review, we present information relating to the effectiveness and safety of the following interventions in primary care and in emergency departments: brief intervention (single- or multiple-session); universal screening plus brief interventions; and targeted screening plus brief interventions.