PURPOSE: To evaluate the clinical outcomes in patients with early-stage non-small-cell lung cancer (NSCLC) after combined treatment with thermal ablation and radiation therapy (RT). MATERIALS AND METHODS: Forty-one patients with inoperable stage I/II NSCLC tumors underwent thermal ablation and RT at our institution between 1998 and 2005. Thirty-seven radiofrequency (RF) ablation procedures and four microwave ablation procedures were performed. Ablations were followed by standard-fraction external-beam RT within 90 days (n = 27) or postprocedural brachytherapy (n = 14). Survival and local recurrence were the primary endpoints evaluated by Kaplan-Meier analysis. RESULTS: The median follow-up was 19.5 months. The overall survival rates were 97.6% at 6 months, 86.8% at 1 year, 70.4% at 2 years, and 57.1% at 3 years. Patients with tumors smaller than 3 cm (n = 17) had an average survival time of 44.4 +/- 5.4 months (SE). Patients with tumors 3 cm or larger (n = 24) had an average survival time of 34.6 +/- 7.0 months (P = .08). Local recurrence occurred in 11.8% of tumors smaller than 3 cm after an average of 45.6 +/- 4.1 months and in 33.3% of the larger tumors after an average of 34.0 +/- 7.8 months (P = .03). Outcomes in the brachytherapy and RT groups did not differ significantly. Nine of 15 pneumothoraces required chest tube drainage (22.0%). CONCLUSIONS: Thermal ablation followed by RT for inoperable stage I/II NSCLC has a relatively low rate of complications that are easily managed. Combined therapy may result in an improved survival compared with either modality alone.