Objectives: To determine the incidence and type of adverse events (AE) in hospitalized patients in Vespucio Clinic, to describe their immediate causes, define avoidable AE and determine the services with highest AE rate Material and method: Retrospective cohort study, in patients discharged between 16 and 31 January 2012. For the identification of AE, medical history was reviewed, and the AE screening guide adapted from the Harvard study was applied. The Spanish version of Modular Review Form MRF2 used in the ENEAS 2005 Study was applied to the patients with positive screening. Results: From the 500 patients studied, 31 had some AE related to health care (6.2%), with an incidence of 3.46 for every 100 patient bed days (minor events 2.72, moderate 0.65, and severe 0.09). The associated processes were: Care 32.4%, medication 13.5%, infections associated with health care10.8%, and diagnostics 8.1%. More than two-thirds (67.6%) were considered avoidable. Of the adverse events, 40.5% required additional procedures, and 35.1% additional treatment. Hospital stay was extended by an average of 5.5 days in 5.4%, and 8.11% led to readmission. Most of them (91.9% did not cause any incapacity. The departments with the highest AE rates per 100 bed patients days were: Critical Care Unit (21.4), obstetrics and gynecology (7), and medical/surgical wards (6) Conclusions: This is the first study conducted in a private hospital in our country that allowed us to identify the incidence, overall rate, and the rate by departments of adverse events, their severity, preventability and causal factors. (C) 2013 SECA. Published by Elsevier Espana, S.L. All rights reserved.