Magnetic resonance (MR) imaging was performed on 37 patients with histologically confirmed astrocytomas (I-III). In addition, the MR tissue parameters T1, T2 and proton density (RHO) were analysed by an interlaced CPMG spin echo sequence. Characteristic morphologic tumour patterns which subdivide astrocytomas into each different tumour grade are presented. Quantitative analysis of MR tissue parameters provides a statistically proven classification of each tumour grade and allows differentiation between "semibenign" astrocytomas (II) and "relatively malignant" astrocytomas (III), with high accuracy.