Background: Approximately 23% of all NSCLC cases in the Netherlands currently undergo a surgical resection. As an increasing number of fit patients have elected to undergo stereotactic body radiotherapy (SBRT) in recent years, we studied outcomes after SBRT in potentially operable stage I NSCLC. Methods: In a single institutional prospective database collected since 2003, 25% of lung SBRT cases (n=177 pts) were found to be potentially operable when the following pts were excluded (1) double lung tumors or other concurrent malignancy, (2) prior high dose radiotherapy/pneumonectomy, (3) COPD GOLD 3-4 (d)WHO score ≥3 (e) co-morbidity precluding surgery. Pts consisted of 101 males and 76 females; median age 76 years; 60% staged as T1 and 40% T2. Median Charlson comorbidity score was 2 (0-5). Patients with no histological diagnosis for a FDG-PET-positive new or growing lesion with CT features of malignancy were accepted as surgical publications report a <4% incidence of benign disease when similar patients undergo surgery in The Netherlands. An SBRT dose of 60 Gy was delivered using a risk-adapted scheme in 3, 5 or 8 once-daily fractions, depending on tumor size and location. Follow-up chest CT scans were obtained at 3, 6 and 12 months, and yearly thereafter. Results: Median follow-up was 32 months; median overall survival (OS) was 61.5 months with 1-, 3- and 5-year survivals of 94.7%, 84.7% and 51.3%, respectively. OS at 3 years in pts with (n=59) and without (n=118) histological diagnosis did not differ significantly (96% versus 81%, respectively, p=0.39). Post-SBRT 30-day mortality was 0%, whereas the predicted 30-day mortality for a lobectomy derived using the Thoracoscore predictive model (Falcoz ’07) would have been 2.6%. Local control rates at 1 and 3 years were 98% and 93%, respectively. Regional and distant failure rates at 3 years were each 9.7%. Toxicity was mild with grade ≥3 radiation pneumonitis and rib fractures in 2% and 3%, respectively. Conclusions: Despite a median age of 76 years, potentially operable pts who undergo primary SBRT have a median OS exceeding 5 years. This finding supports ongoing randomized clinical trials that compare surgery and SBRT in operable stage I NSCLC.