The standard of care for newly diagnosed glioblastoma multiforme (GBM) is temozolomide (TMZ) chemotherapy given concurrently with radiation for 6 weeks followed by 6 months of adjuvant TMZ. Originally, patients in Alberta were treated with only six cycles of adjuvant TMZ regardless of clinical status but institutional policy was amended to allow up to 12 cycles of adjuvant therapy for patients experiencing at least stable disease and minimal toxicity. We conducted a population-based analysis to determine if extended adjuvant TMZ treatment (i.e., more than six cycles) confers a survival advantage as compared to the standard six cycles for newly diagnosed GBM patients. Patient data was collected from the Alberta Cancer Registry and patient charts. Progression free--and overall survival was determined in patients receiving six cycles of adjuvant TMZ and compared with that of patients receiving more than six cycles. Patients in whom adjuvant chemotherapy was stopped at cycle six experienced a median survival of 16.5 months, whereas, those who received more than six cycles survived for 24.6 months (p = 0.031). Extended adjuvant therapy was not associated with increased toxicity. In multivariate analysis, adjuvant monthly Temozolomide for more than six cycles was an independent prognostic factor for both progression free--and overall survival. These data suggest extended adjuvant temozolomide (i.e., more than six cycles) should be considered in patients with newly diagnosed GBM.