Clinical and microbiologic aspects of fungal sinusitis occurring in six patients are presented. Three of the six patients were immunosuppressed. Fatal disseminated fungal disease developed in two of those immunosuppressed. The three patients with normal immune function had fungal infections confined to the nasal sinuses. Aspergillus fumigatus and Aspergillus flavus were recovered from the immunosuppressed patients and Sporothrix schenckii, Alternaria species, and Pseudallescheria boydii were recovered from the immunocompetent patients. Surgical debridement was performed on all patients; however, anti-fungal therapy only was prescribed in patients who were at risk of progressive fungal disease. The microbiology laboratory aids in the diagnosis of fungal sinusitis by examining surgical biopsy material for fungal organisms and by culturing the material for recovery of the fungal pathogen.