Background: Clinical errors in health care can complicate even more a patient's health. In health care systems such as the Colombian it is compulsory to report and follow up such adverse events. Purpose: Describe the frequency and nature of adverse events identified in the clinical records of patients who attended the Endodontics Postdoctoral Clinics of the Pontificia Universidad Javeriana in Bogotá Colombia (2007-2008) and to describe the follow-up reported cases from the first period of 2007. Methods: In this descriptive study, the follow-up chart, radiographic records, and registry in the system (adverse event identification and follow-up model) of 464 clinical records were analyzed to identify adverse events associated with endodontic therapy. Those events could have happened during root canal opening, clean-up/shaping, filling, and post-treatment. Results: There were 306 adverse events related to endodontic treatment (74.4%). 81.3% were preventable events during canal opening (4.1%), clean-up/shaping (36.1%), and filling (60%). Crown perforations, root canal transportation, and overfilling were the most frequent events in the procedures mentioned before. On the other side, there were symptoms reported in 26.3% of the 2007 first-term follow-up cases studied. Conclusion: Since adverse events in endodontics identified in this study were very frequent, it is important to create mechanisms to determine causes and develop strategies to reduce them. [ABSTRACT FROM AUTHOR]