Glioblastoma multiforme are infiltrative lesions that have a high degree of heterogeneity, both within and between different patients. Imaging is critical for all phases in the evaluation and treatment of these lesions, but has been limited in providing information that is reliable enough to stratify patients into groups with uniform behavior and to predict outcome. Although magnetic resonance imaging is the method of choice for visualizing anatomic features of the lesion, its results are ambiguous in terms of defining the functional characteristics of the lesion and distinguishing tumor from treatment induced necrosis. Recent advances in magnetic resonance have made possible the routine acquisition of physiological data such as perfusion- and diffusion-weighted images and of metabolic data such as water suppressed proton spectroscopic images. These provide quantitative measurements that are more closely related to the biological properties of the tumor and reflect changes in tumor vascularity, cellularity and proliferation that are associated with tumor progression. As the molecular properties that influence invasion and neoplastic transformation are elucidated, it is critical that noninvasive imaging techniques are available for investigating new therapies and tailoring treatment to individual patient characteristics. The data obtained from patients with glioblastoma multiforme have already demonstrated that these new magnetic resonance techniques are able to contribute to diagnosis, characterization of malignant potential, treatment planning and assessment of response to therapy.