In recent years there has been a marked increase in mycosis infections of the paranasal sinuses, attributed both to an increase in the survival of subjects at risk and improved diagnostic techniques (endoscopy, CT, MR) able to identify cases which had previously gone unrecognized and treated as aspecific chronic sinusitis. The present study involves 45 cases (4.3%) out of a total of 1050 patients who had undergone endoscopic surgery for sinusopathy between April 1994 and December 1998. Following the Katzenstein classification, the cases were broken down into non-invasive chronic mycoses or fungus ball (34 cases), allergic mycoses (7), chronic indolent invasive mycoses (3) and fulminating invasive mycosis (1 case). The mycetes most often involved was Aspergillus Fumigatus (76.9%). The recurrent symptom was facial algia, followed by nasal obstruction. Paranasal sinuses endoscopy did not modify the specific picture. CT presented such indicative signs as focal areas with non-homogeneous intensity, images of metal-like foreign bodies and endosinus calcifications in 84.4% of the cases. MR--performed in only 6 cases--always presented T2 images showing the typical signal void area corresponding to pathological lesions. All patients underwent endoscopic surgery of the paranasal sinus. The effectiveness of this treatment differed according to the clinical form. In the fungus balls surgery always resolved the pathology without requiring subsequent pharmacological treatment. In allergic mycosis, surgery improved the symptom of nasal respiratory obstruction but local drug treatment was required. With the aid of drug treatment, surgery resolved chronic indolent invasive mycoses and prevented the endocranial progression of complications. In the cases of fulminating invasive mycosis, timely surgery prevented the onset of endocranial complications and made it possible to perform antimycotic polychemotherapy to control the disease. This experience shows how important a protocol involving several different tests is in diagnosing the many clinical forms of paranasal sinus mycoses and distinguishing them from sinusopathies. Endoscopic surgery is indicated for all forms of paranasal sinus mycoses although the realistic objectives differ according to type.