Image-guided SBRT with the delivery of a BED greater than 100 Gy is feasible and safe in the treatment of peripherally located inoperable stage I NSCLC. The 3- to 5-year local control and overall survival rates for SBRT seem to be much better than the rates for conventional radiotherapy, and the toxicity rate is minimal. Particularly for stage Ia (T1N0M0) disease, survival rates with SBRT were comparable with rates seen with surgical resection. SBRT is becoming the standard treatment for inoperable stage I NSCLC. Its role in operable stage I NSCLC. however. is not clear. To balance improved targeting accuracy with minimized treatment-related toxicity. a reliable immobilization device and consideration of image-guided tumor motion are crucial. The optimal dose regimen remains unclear, but a BED greater than 100 Gy seems warranted.