Background: GB is the most common primary brain tumor in adults and has a poor prognosis. Less than 10% of pts are treated on clinical trials. Methods: In this IRB-approved retrospective study, our database was screened for GB pts from 2007-2012. 510 adult patients (pts) with primary GB were identified who participated on a clinical trial. 112 adult pts with primary GB were identified who were clinical trial eligible, but elected not to enroll in a clinical trial. Results: Median age was 54 years (18-83). 307 pts with a primary GB were consented for a newly diagnosed protocol (NDP) and their median OS was 25 months and their median PFS was 12.6 months. Median OS for pts who only enrolled on a recurrent GB protocol (RP) was 19 months from time of diagnosis. These 2 groups had differences in employment, education, symptoms, tumor location, performance status, extent of resection and location of therapy. Pts that were eligible for a clinical trial, but did not enroll, tended to be older, have a lower KPS, live farther away, but had no differences in outcome. Active smokers were less likely to participate in clinical trials. Many pts who enrolled on a clinical trial enrolled in more than one, but receiving dose dense TMZ reduced clinical trial enrollment at recurrence. Age, KPS at presentation, and extent of resection were confirmed as prognostic factors associated with OS. Also, location of radiation therapy (MDACC versus community facility; p=0.02) was associated with OS. 383 pts were identified who either did not follow up for enrollment (n=161, due to distance, evaluation as a second opinion, unknown) or were ineligible for clinical protocols (n=221, prior therapy, early progression or death, treatment toxicity/medical comorbidities, tumor location, insurance denial). Conclusions: Clinical trial eligible GB pts at MDACC have overall better prognoses than historical controls, consistent with other studies. Caution should be taken when interpreting efficacy from single institution, single arm clinical trials. Location of radiation therapy may represent an important variable associated with survival and requires additional investigation. Travel is a significant barrier to clinical trial enrollment.