목적: To compare the clinical outcomes of endoscopic over-underlay tympanoplasty (EODT) and endoscopic overlay tympanoplasty (EOVT) for medium to large size tympanic membrane perforations. 방법:This prospective, single-blinded, randomized controlled trial included 46 patients aged 18-75 years with dry tympanic membrane perforations persisting for at least three months. All patients underwent endoscopic tympanoplasty between September 2023 and July 2024. The primary outcomes were graft success rates and hearing outcomes. Secondary outcomes included operative time and postoperative complications. 결과:A total of 43 patients met the inclusion and exclusion criteria and completed follow-up were analyzed: 22 in the EODT group and 21 in the EOVT group. The overall graft success rate was 95.3%, with no significant difference between groups (EODT: 95.5% vs. EOVT: 95.2%; p = 0.999). Postoperative pure-tone average air conduction (PTA-AC) improved significantly in both groups (EODT: 39.03 +- 13.62 dB preoperatively to 27.84 +- 11.72 dB postoperatively vs EOVT: 36.13 +- 14.26 dB preoperatively to 25.00 +- 12.53 dB postoperatively; p < 0.001). Hearing gain was comparable between groups (p = 0.447). Postoperative air-bone gap (ABG) significantly improved in both groups (EODT: 13.47 +- 7.2 dB preoperatively to 4.26 +- 3.33 dB postoperatively vs EOVT: 12.32 +- 8.33 dB preoperatively to 3.87 +- 3.93 dB postoperatively; p < 0.001), with no significant difference between groups (p = 0.725). Mean operative time was not significant different between groups (EODT: 102.45 +- 13.04 minutes vs EOVT: 104.29 +- 15.43 minutes; p = 0.676). No cases of graft medialization, lateralization, or anterior blunting were observed in either group. 결론:Both EODT and EOVT are effective techniques for repairing medium to large size tympanic membrane perforations, demonstrating high graft success rates and significant audiologic improvement, with no major complications such as sensorineural hearing loss.