Although sinusitis is common, controversy exists regarding terminology, diagnostic criteria, indications for imaging, and treatment guidelines. Patients who are diagnosed with bacterial sinusitis should be started on amoxicillin-clavulanate unless an allergy to penicillin is reported, in which case doxycycline or a respiratory fluoroquinolone is indicated for non-pregnant patients. Patients who fail to respond to antibiotic therapy should be suspected of having chronic sinusitis, which may requirea dditional therapy, including endoscopic surgery. Referral of these patients to an otolaryngologist for further evaluation is recommended. Patients with severe systemic symptoms including altered mental status or severe headaches should be suspected of having fungal sinusitis and to an otolaryngologist acutely because this condition has high mortality if not treated emergently.