Abstract Abstract Background: Percutaneous microwave ablation and radiofrequency ablation are two commonly used modalities for the treatment of hepatocellular carcinoma; however, comparisons of them have not been documented adequately. Methods: Of 102 patients with biopsy-proved hepatocellular carcinoma, 49 (98 nodules) were treated percutaneously with microwave ablation and 53 (72 nodules) with radiofrequency ablation. The local tumor control, complications related to treatment, and long-term results of the two modalities were compared retrospectively. Results: The complete ablation rates were 94.9% (93/98) using microwave ablation vs 93.1% (67/72) using radiofrequency ablation (P = 0.75), and no significant differences were found either in the ablation of tumors of 3.0cm or less (P = 1.00) or in those of more than 3.0 cm (P = 1.00) between the two modalities. The local recurrence rates were 11.8% (11/93) using microwave ablation vs 20.9% (14/67) using radiofrequency ablation (P = 0.12), and there were no significant differences between the two modalities either in tumors of 3.0cm or less (P = 0.36) or in those of more than 3.0cm (P = 0.82). The rates of major complications associated with microwave ablation and radiofrequency ablation were 8.2% (4/49) vs 5.7% (3/53; P = 0.71). The disease-free survival rates in themicrowave ablation group were 45.9% , 26.9% , 26.9% , and 13.4% at 1, 2, 3, and 4 years, respectively, and those in the radiofrequency ablation group were 37.2% , 20.7% , and 15.5% at 1, 2 and 3 years, respectively (P = 0.53). The 1-, 2-, 3-, and 4-year cumulative survival rates for patients who underwent microwave ablation were 81.6% , 61.2% , 50.5% , and 36.8% , respectively, and for patients who underwent radiofrequency ablation the rates were 71.7% , 47.2% , 37.6% , and 24.2% , respectively (P = 0.12). Conclusions: Percutaneous microwave ablation and radiofrequency ablation are both effective methods in treating hepatocellular carcinomas. The local tumor control, complications related to treatment, and long-term survivals were equivalent for the two modalities. Abstract: Background: Percutaneous microwave ablation and radiofrequency ablation are two commonly used modalities for the treatment of hepatocellular carcinoma; however, comparisons of them have not been documented adequately. Methods: Of 102 patients with biopsy-proved hepatocellular carcinoma, 49 (98 nodules) were treated percutaneously with microwave ablation and 53 (72 nodules) with radiofrequency ablation. The local tumor control, complications related to treatment, and long-term results of the two modalities were compared retrospectively. Results: The complete ablation rates were 94.9% (93 / 98) using microwave ablation vs 93.1% (67/72) using radiofrequency ablation (P = 0.75), and no significant differences were found either in the ablation of tumors of 3.0 cm or less (P = 1.00) or in those of more The local recurrence rates were 11.8% (11/93) using microwave ablation vs 20.9% (14/67) using radiofrequency ablation (P = 0.1 2), and there were no significant differences between the two modalities either in tumors of 3.0 cm or less (P = 0.36) or in those of more than 3.0 cm (P = 0.82). The rates of major complications associated with microwave ablation and The disease-free survival rates in these microwave ablation groups were 45.9%, 26.9%, 26.9%, and 13.4% at 1, 2, respectively. The frequency of radiofrequency ablation was 8.2% (4/49) vs 5.7% , 3 and 4 years, respectively, and those in the radiofrequency ablation group 37.2%, 20.7%, and 15.5% at 1, 2 and 3 years, respectively (P = 0.53). The 1-, 2-, , and 4-year cumulative survival rates for patients who underwent microwave ablation were 81.6%, 61.2%, 50.5%, and 36.8%, respectively, and for patients who underwent radiofrequency ablation were 71.7%, 47.2%, 37.6%, and 24.2%, respectively (P = 0.12). Conclusions: Percutaneous microwave ablation and radiofrequency ablation are both effective methods in treating hepatocellular carcinomas. The local tumor control, complications related to treatment, and long-term survivals were equivalent for the two modalities.