Using quantitative MR imaging, values for the mean water diffusivity (<D>), the diffusion anisotropy and the longitudinal relaxation time (T1) were measured for tumour, oedematous and normal brain in a group of treatment-naive patients with high-grade glioma and low-grade meningioma. The mean values of <D> and T1 for enhancing tumour and oedematous brain were significantly higher in high-grade glioma than meningioma, while the diffusion anisotropy was reduced. Values of <D> and T1 were also positively correlated in oedematous brain in both pathologies. There was, however, no clear evidence of similar correlations in apparently normal contralateral white matter. Such results illustrate the potential of MR imaging to improve not only the characterization of brain oedema, but also the monitoring of treatment response.