Objectives To determine the prevalence of alcohol-related presentations in all 29 emergency departments (EDs) in Ireland and compare with non-alcohol-related presentations in order to identify opportunities for improvements in the quality of patient care and related data collection. Design and setting Descriptive prevalence study reviewing all records in the same four 6-hour periods in every 24-hour ED in the country. Participants 3194 persons who attended EDs over four specified 6-hour periods. Primary outcome measures The prevalence of alcohol-related presentations, comparison with non-alcohol-related presentations and the categorisation of these presentations according to WHO International Statistical Classification of Diseases and Related Health Problems 10th Revision codes. Results The total number of presentations was 3194 in the four 6-hour periods, of whom 189 (5.9%) were alcohol related, varying from 29.0% in the early hours of Sunday morning to 1.2% on Monday morning (p>0.0001). The alcohol-related presentations were more likely to be men, attend on early hours of Sunday morning, arrive by ambulance, leave before being seen by a doctor or leave against medical advice; and they were less likely to be admitted to hospital. Conclusions Alcohol-related presentations are a significant burden on EDs and ambulance services, especially in the early hours of Sunday mornings. Addressing the alcohol-related burden on EDs requires improvements in data collection and information systems, the development of appropriate interventions and related referral services and better preventive actions for alcohol-related harm.