Objective: To evaluate incidence and intensity of postoperative pain in patients treated in the Residency Programin Endodontics at the State University of Maringá. The influence of factors inherent to the patient and treatmenton preoperative pain was also the focus of our study. Material and Methods: 99 patients participated in this studyand underwent non-surgical endodontic treatment. Initially, palpation, vertical and horizontal percussion wereperformed on the tooth to be treated. After the root canals filling, patients received a printed Numerical RatingScale and were instructed to record the level of pain in the postoperative periods of 24, 48 and 72 hours. For eachpostoperative period, the patient recorded the values. A descriptive analysis of the data and a model of generalizedestimation equations were performed to verify the relationship between the variables and postoperative pain, ata significance level of 5%. Results: During the follow-up period, the pain rates found were low represented by16%, 11% and 7% in the periods of 24, 48, and 72h, respectively. In addition, the rates significantly decreasedafter 72h. Only one case of flare-up was recorded. Presence of pain on palpation, use of reciprocating file anduse of 2.5% sodium hypochlorite influenced the results (p<0.05), increasing the changes of post-operative painby 3.36, 0.4 and 0.2 times, respectively. Conclusion: Incidence and intensity of postoperative pain monitoredin the residency program reduced significantly after 72 hours. Postoperative pain was associated with pain onpalpation, use of reciprocating files and irrigation with 2.5% hypochlorite.KEYWORDSEndodontics; Postoperative pain; Pain measurement; Endodontic treatment; Root canal therapy.