Stereotactic body radiotherapy (SBRT) for stage I non-small-cell lung cancer (NSCLC) is associated with high local control rates. The impact of introducing SBRT in patients 75 years of age or older was studied using a population-based cancer registry. The Amsterdam Cancer Registry was assessed in three eras: 1999 to 2001 (period A, pre-SBRT); 2002 to 2004 (period B, some availability of SBRT), and 2005 to 2007 (period C, full access to SBRT). χ(2), Kaplan-Meier, and Cox regression were used to compare treatment patterns and overall survival (OS) in three treatment groups: surgery, radiotherapy (RT), or neither. A total of 875 elderly patients were diagnosed with stage I NSCLC in the study period. Median follow-up was 54 months. Primary treatment was surgery in 299 patients (34%), RT in 299 patients (34%), and neither in 277 patients (32%). RT use increased between periods A and C (26% v 42%, P < .01), corresponding to a decrease in untreated patients. The percentage of RT patients undergoing SBRT in periods B and C was 23% and 55%, respectively. Median survival for all patients increased from 16 months in period A to 21 months in period C (log-rank P < .01; hazard ratio HR = 0.65; 95% CI, 0.54 to 0.80). The improvement in OS was confined to RT patients (HR = 0.70; 95% CI, 0.49 to 0.99), whereas no significant survival improvements were seen in the other groups. SBRT introduction was associated with a 16% absolute increase in RT use, a decline in the proportion of untreated elderly patients, and an improvement in OS.