Assessment of vascular proliferation as an important grading criterion has been employed in both the histologic and the radiologic characterization of gliomas with encouraging results. Perfusion in gliomas can be measured by dynamic contrast-enhanced magnetic resonance imaging (dMRI). The goal of this study was to develop a model for simultaneously quantifying the fractional volumes of different tissue compartments of gliomas by dMRI. A modified method for evaluating dynamic contrast-enhanced MR images is presented which simultaneously determines the fractional vascular, interstitial, and cellular volumes of gliomas. This method differs from techniques used in other studies in that it is based on a three-compartment model: a single blood compartment and two interstitial ones. The fractional volume maps are compared with the WHO glioma grading. The results show the method to be feasible. Using cerebral blood volume (CBV), dMRI grading showed a correspondence with WHO grading in 83% of the cases (20/24 gliomas WHO grades II-IV). The use of interstitial volume maps can also be helpful, for instance, in differentiating gliomas from other brain tumors. As a supplement to conventional MRI, dynamic MR techniques thus provide a useful tool for improving in vivo glioma characterization.