Hapatocellular carcinoma (HCC) is one of the most prevalent malignancies in Japan. Percutaneous ethanol injection therapy (PEIT) of microwave coagulation therapy (MCT) have been used to treat small HCC. These two methods are effective methods to treat HCC; however, they have weak points. A period of admission is long to treat patients with PEIT because it requires several sessions to kill HCC completely. The risk of complications of MCT is high because the needle is thick, although it can coagulate HCC completely in one session. Radio frequecy ablation (RFA) is a new method to treat HCC. RFA compensates these weak points and is thought to become a main modality to treat HCC. In this paper, we demonstrated two patients with HCC who were treated with RFA. The effect of the treatment was examined with helical computed tomography and contrast harmonic power doppler, and the results were satisfactory. We also mentioned the merits and demerits of RAF in Discussion.