Magnetic resonance imaging using a 1.5 tesla magnet and a spin echo technique has revealed a remarkably intense signal from abnormal tissue in the human paranasal sinuses. Inflammatory disease in the maxillary, sphenoid, ethmoid, and frontal sinuses has been detected and demonstrated with greater clarity than any other available technique. The pathophysiologic basis for the intense signal has not been defined. These observations do, however, provide an opportunity to discover, clarify, and study paranasal sinus disease. Acute upper respiratory disease, allergic episodes, and the effect of drug treatment based on the MR signal and pathology can now be investigated with this technique. In addition, this may form a basis for assessing the epidemiology of paranasal sinus pathology.