In recent years there has been an increase in fungal infections of the nose and paranasal sinuses, even though it is difficult to ascertain the incidence and prevalence of such disorders. The only information which can be drawn from the literature is that such infections are diagnosed in 6% to 13% of surgically treated chronic sinusitis. Aspergillus is the etiologic agent in approximately 80% of cases. Fungal infections are classified into two groups: non-invasive and invasive. The former includes mycetoma and allergic fungal sinusitis. The latter comprises the chronic indolent form, which presents slowly progressive bone erosion, and the fulminant form, which almost invariably carries a dismal prognosis. The maxillary sinus is involved in 80% of mycetomas, followed, in order of frequency, by the ethmoid and frontal sinus. Localization in the sphenoid sinus is exceedingly rare, with only 71 cases reported in the literature. Diagnosis of mycetoma is based on fungal cultures of nasal secretion (which are indeed of limited sensitivity, around 40%) and histological examination of the material removed from the sinus, which identifies the fungus in 80% of cases. CT and MR are highly sensitive diagnostic tools because of their ability to detect the presence of ferromagnetic substances (i.e. iron, magnesium and manganese) and calcium deposits in the diseased sinus. Four new cases of sphenoid mycetoma, treated with endoscopic surgery, are described. The advantages of the endoscopic approach compared to traditional techniques and the role of anti mycotic agents are also discussed.