Aims: To evaluate the relationship between preoperative resting arterial blood pressure and postoperative pain in patients undergoing nonsurgical root canal therapy. Methods: Written informed consent was obtained from normotensive patients seeking treatment for teeth with a preoperative diagnosis of pulpal necrosis and periradicular periodontitis. Preoperative resting blood pressure was recorded, and nonsurgical root canal therapy was initiated using a standardized protocol. Patients recorded their pre- and postoperative pain intensity on a 100-mm visual analog scale (VAS) for 7 days after the procedure. A linear regression model to predict postoperative VAS intensity used preoperative pain and blood pressure values as covariates. Pearson correlations were calculated to assess the relationship between the measures of preoperative blood pressure and both pre- and postoperative pain. Results: After controlling for preoperative pain, significant correlations were observed between preoperative systolic blood pressure and postoperative pain (P .05), as well as between preoperative pulse pressure and postoperative pain (P .005) on day 1. Conclusion: This study has provided further evidence of a functional interaction between the cardiovascular and trigeminal pain regulatory systems. Understanding this complex relationship may lead to enhanced pain management strategies. Schlagwörter: blood pressure, cardiovascular system, endodontics, orofacial pain