The failure of conventional therapies for many malignant brain tumors has led to a search for more promising alternatives. Recent advances have elucidated a variety of biological factors that act to determine the growth and invasiveness of central nervous system tumors. Such factors include aberrations in the regulation of the cell cycle, apoptosis, and interactions with the host microenvironment. Such insights should translate into novel interventions so that more meaningful outcomes can be achieved in patient care in the future.