Purpose: The aim of this study is to describe the safety and efficacy of radiofrequency ablation (RFA) in the treatment of unresectable liver metastasis from colorectal cancer. Methods: From January 1999 to December 2000, we undertook 48 RFA procedures in 36 patients with unresectable metastatic liver tumor from colorectal cancer. RFA was performed either via celiotomy (n=23) or using a percutaneous approach (n=25) under ultrasound guidance using a LeVeen needle electrode and a RF 2000 generator. Patients were followed with spiral computed tomographic scans at 1 week after RFA. Results: RFA was performed in 15 patients with synchronous hepatic metastasis and 21 with metachronous hepatic metastasis. The mean tumor size was 3.1 ㎝ (range; 0.5∼7.2 ㎝). In 2 patients, complete ablation failed due to anatomic tumor location. Nine patients (25%) exhibited post RFA complications (9 cases of fever, 8 of abdominal pain, and 1 of hematoma) which showed spontaneous resolution and there was no treatment-related death. At a mean follow up of 10.1 months, 12 patients (33.3%) had recurred in the liver and 3 (8.6%) at the RFA site, while 16 (44.4%) remained clinically free of disease. Conclusion: Although RFA is a relatively safe procedure in patients with unresectable hepatic metastasis from colorectal cancer, the possible development of new metastatic disease after RFA is currently a limitation in this form of treatment. Further study on the efficacy of RFA versus other treatment modalities is needed.