Patient safety is an issue of interest. All scenarios of health care have a risk of adverse events (AE) and determination of its incidence has been reported in virtually all medical specialties. Objective: To determine the incidence reported in the medical literature of adverse events in medical departments. Design and methods: An exhaustive search of biomedical databases using different strategies, search in high impact journals and a manual search of related articles. Results: We reviewed 17,437 entries. After reading the abstracts and articles, and applying previously defined inclusion and exclusion criteria, we selected 10 articles that reported the incidence of adverse events in medical departments. Most studies corresponded to a historical cohort, had used an AE screening to identify high risk patients, and had used a structured review to check clinical records. None of them had as their ultimate objective to report on the impact of adverse events or characterize them. The incidence reported in medical departments ranged from 3.6% to 21.7%. The definitions of adverse events and forms of detection were similar; however the few differences put the comparability at risk. Conclusion: No studies were aimed at quantifying or characterising the adverse events in health care. None of them defined what constitutes a medical department, although the results reported are within the published values for health systems. Further research is needed in this area. © 2011 SECA. Published by Elsevier España, S.L. All rights reserved.