Fifty patients with a wide range of sinus disease have been examined by magnetic resonance. These included congenital conditions, inflammatory and allergic sinus disease, fungus infection, and both necrotising and non-necrotising granulomas. A variety of benign and malignant tumours have been investigated, including eight examples of juvenile angiofibroma and 19 malignant sinus tumours. This experience of magnetic resonance scanning has shown that it is superior to computed tomography in showing the extent of malignant disease and, provided the correct pulse sequences are employed, it is always possible to distinguish tumour from retained secretion or inflamed mucosa. The extent of intracranial invasion can also be optimally demonstrated. One of the advantages of the method is the direct three-plane imaging and multislice technique, which gives total coverage of the head and neck for the assessment of malignant disease. Tissue diagnosis in the paranasal sinuses is less important than the demonstration of tumour extent and distribution. Only one tumour (juvenile angiofibroma) showed diagnostic spin-sequence characteristics, and no differentiation was observed between malignant tumours of epithelial and mesenchymal origin. The major drawback of magnetic resonance is the poor demonstration of bone and calcification in the sinuses, so that in some patients the scans need to be augmented by computed tomography studies.