Gliomas encompass a wide variety of particularly devastating tumors, for which efficient therapies are not available. Their etiology remains mostly undetermined: so far, only exposure to high dose therapeutic radiation has been firmly established as a risk factor, but other plausible causes include genetic syndromes, familial aggregation, and genetic polymorphisms. The clinical performance status and patient age at diagnosis are definite features associated with outcome, but recent evidences suggest that tumor's molecular traits are also major determinants of prognosis. This book aims to review and discuss how molecular determinants may affect glioma risk and patient outcome, with a very special emphasis in glioblastoma multiforme, the most common and malignant glioma subtype. To do so, Part I presents a general introduction that summarizes the classification, epidemiology, and treatment of gliomas, while devoting particular attention to potential etiological factors and molecular alterations of these tumors. Part II presents original research studies emphasizing the relevance of particular biomarkers of glioma, particularly at the levels of glioma risk and patient prognosis.