In the past few decades the incidence of mycotic infection of the paranasal sinuses has increased considerably, primarily because of the expanded use of antibiotics and chemotherapeutic agents, such as folic acid antagonists and nitrogen mustards. Clinical awareness of the existence of mycotic infection and advancement in the knowledge and technic of fungus identification also account for the rising incidence. When interpreting a roentgen examination of the paranasal sinuses, the radiologist may see mucous membrane thickening, clouding of the sinuses, and bone destruction. These changes may occur in malignant tumors and in bacterial or mycotic infection. Case Reports Case I: A. B., a 68-year-old white man, was admitted to Bellevue Hospital on Aug. 4, 1959, with a history of recent bloody discharge from the left nostril, associated with erythematous swelling and tenderness over the left maxillary and orbital regions. There was a long history of poorly controlled diabetes. The only significant laboratory st...