43 patients with malignant tumours of the larynx or hypopharynx were examined by MRT and CT to compare their accuracy for T-staging. There was histological confirmation in all cases. Histological studies showed an accuracy in T-staging of 90% for MRT and 82% for CT. Differentiation between stages T2/T3 and T3/T4 is possible in most cases by either method. A source of error is the difficulty of differentiating oedema or inflammatory changes from tumour. This led to occasional overinterpretation of the T4 stage. Demonstration of cartilage involvement was easier with MRT (88%) than with CT (84%). The use of Gd-DTPA with T1 weighted and proton weighted sequences allows earlier diagnosis of cartilage invasion. Early cartilage involvement may be missed by CT when it is seen on MRT. In addition, the ability to produce coronal and sagittal images by MRT makes this superior to CT in judging tumour extension.