Aim: To determine if enrollment on glioblastoma (GBM) interventional clinical trials (ICTs) in the USA is representative of the population. Materials & methods: We queried ClinicalTrials.gov for all ICTs in GBM from 1994 to 2019. Demographics were obtained from ClinicalTrials.gov or the trial publication and compared with population data from Central Brain Tumor Registry of the United States. Results: In total, 10617 GBM patients were enrolled in 118 adult ICTs: median age was 54.0 (10.05 years younger than Central Brain Tumor Registry of the United States). Age was most discrepant in recurrent tumors, nonrandomized trials and consortium studies. Median age improved from 52.0 to 59.5 over 25 years. Women represented 37.5% of subjects. Conclusion: GBM ICTs under-represent older patients but representation of women reflects the population. ICTs need to be designed to better represent the population.