OBJECTIVE: The records of the emergency room of Landspitali University Hospital in Iceland provide important information on the prevalence and incidence of various problems. The objective of this research is to evaluate the reliability of data concerning the visits of adolescents under the influence of alcohol. Data AND METHODS: Records of visits to the Emergency Room of Landspitali University Hospital by 14-16 year old capital region adolescents are compared with the results of a survey in early 2003. The correspondence between hospital records and adolescent self-reports is compared to the correspondence between records and self-reports of the presence of alcohol in visits. RESULTS: In all cases students report more emergency room visits than are recorded by Landspitali University Hospital. The difference is 4.2% (+/- 0.6%) in accident visits and 2.2% (+/- 0.2%) in violence visits. In the case of the presence of alcohol in visits the difference is 9.3% (+/- 0.4%) between hospital records (0.2%) and adolescent self-reports (9.5%). CONCLUSION: The records of Landspitali University Hospital are not a valid source of information on alcohol-related problems among adolescents. About one in ten adolescents in the capital region of Iceland claim to have visited an emergency room because of their own alcohol consumption but hospital records of the presence of alcohol only include about 1/60 of that number.