Radiofrequency ablation (RFA) is a new, minimally invasive treatment for hepatocellular carcinoma (HCC). However, there is little available information regarding local recurrence after a single session of RFA with a single electron insertion. From February 1999 to September 2001, we treated 104 HCC tumors with an expandable needle with four hooks. Ninety-nine of the 104 tumors were successfully treated by single-session RFA with a single electrode insertion. We investigated the relationships between pretreatment factors (tumor size, tumor staining, tumor capsule, and tumor location) and local recurrence in these 99 tumors. The mean size of the 99 tumors was 21.5 mm in diameter (range, 10 to 33 mm). The overall local recurrence rates were 9.7%, 15.4%, and 20.4%, at 1, 2, and 3 years, respectively. For small tumors (smaller than 25 mm), the local recurrence rates at 1, 2, and 3 years were 4.0%, 8.0%, and 14.6%, respectively. The local recurrence rates were 21.1% and 32.3% at 1 and 2 years, respectively, for large tumors (25 mm or larger), and at 3 years the rate was over 50% for tumors located close to the liver surface. Tumor size and tumor location relative to the liver surface were significantly associated with a higher local recurrence rate. However, other variables tested showed no significant relationship to the local recurrence rate. This study demonstrated that both tumor size and location relative to the liver surface influence the local efficacy of single-session RFA with a single electrode insertion.Radiofrequency ablation (RFA) is a new, minimally invasive treatment for hepatocellular carcinoma (HCC). However, there is little available information regarding local recurrence after a single session of RFA with a single electrode insertion.