Objective: The purpose of the present study was to compare the selection criteria and short-term outcomes among 3 prospective clinical trials using stereotactic body radiotherapy (Radiation Therapy Oncology Group [RTOG] trial 0236), sublobar resection (American College of Surgeons Oncology Group [ACOSOG] trial Z4032), and radiofrequency ablation (ACOSOG trial Z4033). Methods: The selection criteria and outcomes were compared among RTOG 0236 (n = 55), ACOSOG Z4032 (n = 211), and ACOSOG Z4033 (n = 51). Age, Eastern Cooperative Oncology Group performance status, percentage of predicted forced expiratory volume in 1 second, and percentage of predicted carbon monoxide diffusing capacity of the lung were used to perform a propensity-matched analysis among patients with clinical stage 1A in RTOG 0236 and ACOSOG Z4032. Results: The patients in ACOSOG Z4033 undergoing radiofrequency ablation were older (75.6 ± 7.5 years) than those in RTOG 0236 (72.5 ± 8.8 years) and ACOSOG Z4032 (70.2 ± 8.5 years; P = .0003). The pretreatment percentage of predicted forced expiratory volume in 1 second was 61.3% ± 33.4% for RTOG 0236, 53.8% ± 19.6% for ACOSOG Z4032, and 48.8% ± 20.3% for ACOSOG Z4033 (P = .15). The pretreatment percentage of predicted carbon monoxide diffusing capacity of the lung was 61.6% ± 30.2% for RTOG 0236, 46.4% ± 15.6% for ACOSOG Z4032, and 43.7% ± 18.0% for ACOSOG Z4033 (P = .001). The overall 90-day mortality for stereotactic body radiotherapy, surgery, and radiofrequency ablation was 0%, 2.4% (5/211), and 2.0% (1/51), respectively (P = .5). Overall, the unadjusted 30-day grade 3+ adverse events were more common with surgery than with stereotactic body radiotherapy (28% vs 9.1%, P = .004), although no difference was between the 2 groups at 90 days. Among the patients with clinical stage IA in ACOSOG Z4032, 29.3% had a more advanced pathologic stage at surgery. A propensity-matched comparison showed no difference between stereotactic body radiotherapy and surgery for 30-day grade 3+ adverse events (odds ratio, 2.37; 95% confidence interval, 0.75-9.90; P = .18). Conclusions: Among appropriately matched patients, no difference was seen in early morbidity between sublobar resection and stereotactic body radiotherapy. These results underscore the need for a randomized trial to delineate the relative survival benefit of each modality and to help stratify patients considered high risk.