The authors report on 178 patients with unresectable hepatic tumors who have been treated with 1 to 25 (median, 6) courses of radiofrequency hyperthermia (RFHT) and chemotherapy. In 137 patients, the hepatic tumors consisted of metastases from colorectal adenocarcinomas. For patients who had no previous therapy and who had colorectal metastases with no extraheptic disease, cumulative survival at 52 weeks' follow-up was 80.5% and partial tumor regression was seen in 78.4%. Among the 69 patients who previously had conventional treatment for their hepatic disease, partial regression was seen in 43.5%. We are no longer monitoring tumor core temperature routinely, as the invasive methods currently in use yield irreproducible results; the risks to the patient cannot be justified in view of the questionable relevance of the data obtained. A prospective randomized study of systemic chemotherapy with or without RFHT in patients with colorectal hepatic metastases is in progress.