Objectives: The aim of this study was to asses the influence of the shaping technique on incidence, intensity, duration and type of postoperative pain (PP). Methods: Root canal treatments were carried out with rtary instrumentation (n=80) during a single-visit, and data about pre-treatment conditions were collected. Patients were given a questionnaire to record the presence or absence of post-endodontic pain, its duration and level of discomfort. A matching patient (same pre-treatment conditions but manual instrumentation) was randomly selected from a pool (n=374) and assigned to the control group. A total of 44 pairs of patients matched completely and were included in the study. Incidence (yes/no) of PP was assessed using Chi-square tests, intensity (mild, moderate, severe) with trend tests and duration (days) with Mann-Whitney U tests. Results: A significantly greater proportion of the patients in the control group reported pain than did patients in the rotatory shaping group (p