The aim of this study was to evaluate the usefulness of RF interstitial thermal ablation for treating hepatic cancer. Fifty patients, 39 who had 41 hepatocellular carcinoma nodules and 11 who had 13 hepatic metastatic nodules, underwent RF interstitial thermal ablation. In all but one, a thermal necrosis volume greater than the tumoral nodule volume was created to obtain total tumor destruction. One large tumor was treated for debulking purposes. Hepatocellular carcinoma nodule destruction was achieved in a mean of 3.3 sessions of RF interstitial thermal ablation. During a mean follow-up of 22.6 months (range, 3-66 months), 16 (41%) of 39 patients had recurrences; two (5%) of these patients showed local recurrences and the remaining 14 (36%) had new lesions. Nine of these 16 patients underwent further RF interstitial thermal ablation that proved effective. RF interstitial thermal ablation was also successfully repeated in four patients who had a second recurrence. With RF interstitial thermal ablation, we treated 54 hepatocellular carcinoma nodules in 39 patients. Eleven (28%) of the 39 patients died: five from hepatic failure due to advanced cancer and six from causes other than cancer. Autopsy was performed on three patients who died from causes other than cancer, one had had two new courses of RF interstitial thermal ablation for two new lesions. Gross examination failed to detect two treated tumor nodules; histologic examination of three other treated tumor nodules showed total necrosis in two nodules and a 3-mm focus of viable cancer cells in the other nodule. Cumulative survival curves showed the median survival time to be 44 months. The survival rate for the first year was 0.94, 0.86 for the second year, 0.68 for the third year, and 0.40 for the fourth and fifth years. In the patients treated for metastatic nodules, posttreatment imaging studies showed necrosis that varied from 80% to 100% in all cases. Pathologic studies performed on two patients who underwent surgery after RF interstitial thermal ablation showed 100% necrosis in one case and 80% necrosis in the other. RF interstitial thermal ablation is a useful percutaneous treatment for hepatic cancer.