Background: The aim of the present pilot study was to assess the bactericidal efficacy of a high frequency diathermy irradiation in treatment of teeth with diagnosed partial pulp necrosis. Methods and Results: The study included 83 patients aged between 22 and 54 years (mean age of 39 +/- 10 years) with irreversible pulpitis and signs of partial pulp necrosis in multi-rooted teeth (n=83). All patients were randomized in two groups in accordance with conducting therapy modes: 1) a conventional root canal treatment (Group 1, n=40); 2) a conventional treatment protocol in conjunction with a high frequency diathermy irradiation (Group 2, n=43). The postoperative sensitivity of treated teeth was assessed with the help of the Verbal Rating Scale (VRS). The quality of a root canal disinfection was evaluated by the presence of a cultural growth. The periapical index scoring system (PAI) was used for evaluation of periapical changes in every tooth after endodontic therapy. The occurrence of postoperative pain in Groups 1 and 2 demonstrated a similar reduction in toothache dynamics at all time intervals when assessments were made, and analysis of tooth radiographs in both groups of patients did not reveal a significant difference. As for the evaluation of a cultural growth, the signs of turbidity were detected in 6 samples of Group 1 and in 4 samples of Group 2. Conclusion: The possible antimicrobial efficacy of a high frequency diathermy in treatment of teeth with partial pulp necrosis was demonstrated. However, further studies should be made to confirm the results of this clinical trial.