Oligodendrogliomas have been the focus of considerable interest over the last decade, ever since they were recognized as chemosensitive tumors. However, the histological diagnosis remains highly controversial and unsatisfactory. Meanwhile, our understanding of glioma oncogenesis improved greatly. Gliomas are the consequence of specific genetic or epigenetic alterations - activations of oncogenes and inactivation of tumor suppressor genes - resulting in the disruption of critical cellular pathways and leading to phenotypic changes. Such genetic information complements the existing WHO morphological classification and, more importantly, provides additional prognostic markers. Indeed, 1p/19q deletion has been correlated with chemosensitivity in oligodendrogliomas, and is becoming more and more widely used in clinical practice. There is little doubt that emerging techniques, such as CGH-array and gene profiling will be very helpful in clinical practice for refining both classification and therapeutic indications of oligodendroglial tumors.