Objectives/Hypothesis: To investigate the morbidity and mortality of patients undergoing endoscopic sinus surgery (ESS) in the inpatient setting.Study Design: Retrospective database review. Methods: The Nationwide Inpatient Sample was queried for all ESS between 2008 and 2014. Using All Patients Refined Diagnosis Related Groups (APR-DRG) codes, cases with APR-DRG codes under Major Diagnostic Category 3 (Diseases and Disorders of the Ear, Nose, Mouth, and Throat) were designated as patients with primary otolaryngology diagnoses undergoing ESS (ORL), and all other codes were designated as patients with non-otolaryngology pathologies as their primary reason for admission but undergoing ESS (non-ORL). A univariate analysis and a logistic regression were used to compare patient demographics, comorbidities, disease severity, and mortality.Results: There were 8,305 ORL patients and 6,342 non-ORL patients. ORL patients were more likely to be elective admissions (61.3% vs. 48.5%, P < .001), have a deviated nasal septum (17.9% vs. 12.3%, P < .001), nasal polyps (15.8% vs. 5.0%, P < .001), obstructive sleep apnea (10.7% vs. 5.2%, P < .001), and pulmonary disease (15.9% vs. 10.5%, P < .001). Non-ORL patients had a higher likelihood of in-hospital mortality (odds ratio [OR] 6.22, 95% confidence interval [CI] 3.29-11.78, P < .001), length of stay in the highest quartile (OR 2.43, 95% CI 2.16-2.74, P < .001), and a higher proportion had APR-DRG subclasses indicating extreme severity of illness (19.3% vs. 4.3%, P < .001) or extreme risk of mortality (12.5% vs. 2.0%, P < .001).Conclusion: Patients undergoing ESS in the inpatient setting have a higher than expected mortality rate which can be associated with a non-otolaryngology pathology as the primary reason for their admission.