Thirty-one patients with sphenoid sinusitis were treated from 1978-1982. Twenty patients had infections contiguous with other paranasal sinus disease. Five of these patients had fungal sinusitis. Eleven patients were seen with isolated sphenoid sinusitis; 3 were secondary to trauma and 8 were due to nontraumatic causes. Possible etiologies include upper respiratory infections, developmental abnormalities, and water forced into the nasal cavity during swimming. The immunocompromised patient is more likely to present with minimal symptoms with a fungal infection, and aggressive diagnostic and therapeutic measures should be undertaken. Because the symptoms of headache, nasal stuffiness, proptosis, ptosis and decreased visual acuity may be interpreted as an intracranial, neurological, or vascular problem, a misdiagnosis may be made. A high index of suspicion for sphenoiditis should be maintained. Therapy involves a combination of medical (antimicrobial agent) and surgical (sinus drainage and marsupialization) management.