For medically operable patients with stage I non-small-cell lung cancer (NSCLC), lobectomy or pneumonectomy remains the standard of care. The utility of radiotherapy or chemotherapy after major pulmonary resection remains unproven, though clinical and biological models may identify subgroups most likely to benefit. Limited resection results in higher rates of local failure for all but the most highly selected patients, though brachytherapy may reduce this risk. In medically inoperable patients, conventional radiotherapy results in control rates less than half of that achieved by surgery. Dose escalation and hypofractionation are technically feasible with modern planning and delivery, and appear to improve control rates compared with conventional radiotherapy. Stereotactic body radiotherapy represents a major advance for the treatment of stage I NSCLC, with early reports documenting excellent control rates and a low risk of severe toxicity. In this review we address each of these points, with particular emphasis on recent or ongoing prospective trials.