Background: Glioblastoma multiform (GBM), the most aggressive CNS cancer, has limited effective therapeutic options, with underlying molecular heterogeneity contributing to the differences in treatment response. Our study was designed to interrogate biomarkers from a large cohort of GBM patients to seek therapeutic implications. Methods: Data was analyzed from 570 high grade astrocytoma patients (vast majority GBM) who received tumor profiling at Caris Life Sciences from 2009 to 13. Test methodologies included IHC, FISH, CISH, Sanger SEQ, MGMT promoter methylation and NextGen SEQ (Illumina TruSeq). Results: In our patient cohort, 59% had MGMT methylation and 70% had negative MGMT IHC, predicting potential response to temozolomide. Protein expression for ERCC1, TOPO1, and TS was 53% negative, 49% positive, and 37% negative, indicating potential benefit from cisplatin, irinotecan and fluorouracil, respectively. Drug pumps PGP and MRP1, were positive by IHC in 10% and 67% of patients, suggesting possible resistance to etoposide, vinca alkaloids and methotrexate. For targeted therapies, c-Kit IHC was positive in 7% patients, mutated in 6% and PDGFRA IHC was positive in 27%, indicating potential benefit from imatinib and other TKI’s. RAS/RAF and PIK3CA/mTOR pathway activation was also noted with BRAF, KRAS, PIK3CA mutations and PTEN loss, observed in 8%, 3%, 7% and 10% of cases, respectively. TS negativity was seen in 91% of MGMT methylated patients and in 37% of MGMT unmethylated patients (p = 0.025, student’s t-test), revealing a possible novel combination therapy of fluoropyrimidines with temozolomide for a select cohort. Similarly, biomarker profiles of molecular subgroups defined by EGFR amplification (44% in our cohort) and IDH1, p53 mutations will be analyzed for therapeutic implications. Conclusions: By profiling tumor biomarkers from a large cohort of GBM patients using validated assays in a single facility, we demonstrate the vast molecular heterogeneity of GBM and highlight the importance of individualized therapy based on a patient’s unique tumor profile. Incorporating a comprehensive biomarker analysis into clinical management of this aggressive cancer allows for an informed selection of more effective therapies.