Aspergillosis of the paranasal sinuses appears to be relatively rare in occurrence, but there is a growing incidence of it in accordance with the increasing use of antibiotics, steroid hormones, anticancer drugs, and radiation therapy. We have seen 15 cases of aspergillosis of the paranasal sinuses in which computed tomography (CT) was helpful for diagnosis. The characteristic feature of CT findings was the intermixture of high and low density areas in the affected paranasal sinuses, apparently caused by increased X-ray absorption due to calcification. These findings indicate that CT is useful in the preoperative diagnosis of aspergillosis of the paranasal sinuses.