Radiofrequency ablation (RFA) therapy combined with hepatectomy was performed in 5 patients with synchronous liver metastases of colorectal cancer. RFA of liver metastases was performed using a Cool-tip electrode (Radionics; Burlington, MA, USA). The ablation time used in each session varied according to the tumor size and intraoperative impedance. In 2 patients, hepatectomy and resection of the colorectal primary lesion were performed synchronously. In patients with multiple liver metastases, relative curative resection was performed using the complementary RFA. In the other 3 patients, synchronous hepatectomy was considered difficult and systematic chemotherapy was performed after resection of the colorectal primary lesion. After systematic chemotherapy, the range of hepatectomy was restricted for liver injury, but relative curative resection was performed using RFA therapy. Computed tomography performed after hepatectomy showed that the region that underwent RFA appeared necrotic with a safety margin. The average observation period was 25 months (maximal survival period, 50 months) and 3 of the patients are alive.