Over the last decade, we have observed a high frequency of Aspergillus rhinosinusitis in french medical centers. The epidemiological data, clinical presentations, radiology, mycology and histology results of 173 consecutive patients with paranasal sinus fungus balls who were admitted from 1989 to 2002 have been reviewed. The most common symptoms included purulent nasal discharges and nasal obstructions, with the maxillary sinus being the most common site of infection (152 cases, 87.8%). Computed tomography scans (CT scan) were performed in 92% (159/173) of the cases and heterogeneous opacities were observed in 132 patients (83%). Histology examinations were performed in all cases and proved positive in 162 patients. Fungi were recovered, mainly Aspergillus fumigatus, from samples of 50 patients, while specimens from the remaining 123 patients were negative. Since no specific clinical sign could be found, a diagnosis of fungus ball is frequently made after a long term symptomatic period. CT scan findings of metallic or calcified densities within an opacified sinus cavity are highly suggestive of a fungus ball, but mycological and histological studies are essential to confirm the diagnosis. Treatment consisted of functional endonasal sinus surgery and was successful in 172 out of 173 cases.