We report the computed tomographic appearance of invasive fungal disease of the paranasal sinuses in 13 patients. Coronal and axial computed tomographic images were obtained in each patient and data were analysed. Eight patients had Aspergillus flavus infection, four had Mucormycosis, and one had mixed Candida and Mucor. Our experience was different from that of other workers in many respects. All of our patients were immunocompetent. On radiological imaging by computed tomography, ethmoid sinuses were involved in 85% of our patients. In previously reported series maxillary sinuses were most frequently affected. Calcification in the inflammatory mass was not encountered in any of our patients, whereas this feature was present in many reported cases. Features in our patients that were similar to other studies were contrast enhancement, extension of the disease into the orbit and cranial cavity and a high mortality. The clinical course and radiological features of invasive mycosis simulate malignancy. Certain features that may help to differentiate invasive fungal infection from malignancy are discussed. We conclude that invasive fungal infection can affect immunocompetent individuals and should be considered in the differential diagnosis in appropriate clinical settings.