Background and Objectives: Gliomas are the most prevalent primary brain tumors. The purpose of this retrospective cohort study was evaluation of clinical trend and prognosis of patients with brain glioma and effective factors in prognosis. Materials and Methods: Hundred and forty-five patients with supratentorial brain glioma, treated in Shahid Mostafa Khomeini & Hazrat-e-Rasool hospitals in Tehran , Iran from March 1999 to August 2005, were studied. Clinical, therapeutic and malignancy grade data were collected. The WHO classification was used for reporting malignancy grade. All patients were pursued until August 2005. Mann-Whitney, Kaplan-Meier, Cox Regression, and Chi-Square test were used for analysis. Results: Median survival was 39.7 weeks for malignancy grade IV. One-year survival rates in malignancy grades of II, III, IV and all patients were 86%, 83%, 40% and 47%, respectively. In multivariate analysis, effective factors in prognosis of all patients above 60 were radiotherapy and malignancy grade IV; and in patients with malignant glioma were age of above 60 and radiotherapy; and in patients with low-grade glioma were motor deficits. Conclusions: Survival rate decreases from malignancy grade II to IV and this reduction is evident in malignancy grade IV. Role of radiotherapy as an effective factor in prognosis in all patients and in malignant glioma is important.