Malignant disease of the paranasal sinuses is not common. During a period of approximately 25 years only 62 cases have been seen at the University of Chicago Clinics. The series includes only tumors considered to have originated within the sinuses. Tumors of the nose, palate, orbit, skin, or intracranial structures which have invaded the sinuses have been excluded. Characteristics Origin of Tumors. —All lesions in this series originated in the antrum or ethmoids. There were no primary growths of the sphenoids or frontal sinuses, but these were, however, occasionally involved with tumor secondarily. Age. —Two patients were in their 20's and two were in their 30's when first seen. Sixteen were in the 40 to 49 age groups; fourteen, in their 50's; twenty-one, in their 60's, and seven were 70 or over. Sex. —Thirty-four patients were men, and twenty-eight were women. Side of Growth. —In 40 cases the tumor was