OBJECTIVE: This study aimed at retrospectively evaluating the outcomes of radiofrequency ablation of clinical stage I non-small cell lung cancer. METHODS: This study was carried out on 50 nonsurgical candidates (29 men and 21 women; mean age, 74.7 years) with clinical stage I (IA, n = 38; IB, n = 12) histologically proven non-small cell lung cancer. A total of 52 tumors were treated with 52 ablation sessions. Radiofrequency ablation was performed percutaneously under computed tomography fluoroscopic guidance. The outcomes of radiofrequency ablation were evaluated, including toxicity, local efficacy, and patient survival. Toxicity was evaluated using the National Cancer Institute Common Terminology Criteria for Adverse Events Version 4.0. Local efficacy was evaluated by using computed tomography scan with a contrast medium. The overall, cancer-specific, and disease-free survivals were estimated with Kaplan-Meier analysis. RESULTS: Grade 2 and 3 adverse events occurred after 6 (12%) and 3 (6%) of the 52 sessions, respectively. The median follow-up period was 37 months. Local progression was observed in 16 (31%) of the 52 tumors. The median survival time was 67 months. The overall, cancer-specific, and disease-free survivals were 94%, 100%, and 82% at 1 year, 86%, 93%, and 64% at 2 years, and 74%, 80%, and 53% at 3 years, respectively. CONCLUSIONS: Radiofrequency ablation of clinical stage I non-small cell lung cancer was minimally invasive and provided promising patient survival, although the local efficacy needs to be improved.