Background: Up to 50% of advanced NSCLC patients receive radiation therapy at some point in their course. We sought to determine whether patients with prior radiation demonstrate altered outcomes on subsequent metastatic clinical trials. Methods: We reviewed 8 ECOG-ACRIN advanced non-small cell lung cancer studies conducted between 1993 and 2011 in which information was collected about receipt of prior radiation. Whether radiotherapy was given with curative or palliative intent, or to specific sites was not recorded. Median follow-up among all trials was 66 months. We used the log-rank, Wilcoxon and Fisher’s exact tests to compare patients, and Cox Model and Kaplan-Meier method to calculate survival. Results: 574/3041 (18.9%) patients had received prior radiation. These patients were more likely to be male (64% vs 58%), have squamous histology (20% vs 14%) and have had prior surgery (48% vs 33%) compared to those with no prior radiation. At registration, prior radiation patients were more likely to have an ECOG PS of 1 (66% vs 58%), while they were less likely to have a PS of 0 (24% vs 36%) or have a pleural effusion (23% vs 37%). Patients who received radiation were more likely to have been registered on to studies between 1993-1999 than 2000-2011 (69% vs 31%) (all p < 0.001). Median Overall Survival (OS) for patients with prior radiation was 7.6 months (range 7-8.3) vs 9.5 (9.1-9.8) for those without (p < 0.001). Median Progression Free Survival (PFS) for those with prior radiation was 3.5 months (3-3.9) vs 4.2 (4.1-4.4) for those without (p < 0.001). In multivariable analysis controlling for stage IIIB/IV, sex, PS, histology, and prior surgery, the impact of prior radiation on overall survival remained significant (p = 0.042, HR (95% CI) = 1.11 (1.00, 1.22)). Conclusions: Almost one-fifth of lung cancer patients on systemic therapy trials for advanced disease previously received radiation. They are more likely to be male, have squamous histology, have an ECOG PS of 1 and have had prior surgery. Prior radiation is significantly associated with inferior OS and PFS. For advanced NSCLC clinical trials, documentation of whether curative intent/palliative intent radiation was given and stratification by prior radiation exposure should be considered.