['Postoperative adhesion formation after endoscopic sinus surgery (ESS) remains a complication associated with high revision rates. This study determines the efficacy of a sprayable chitosan/starch-based sealant for reducing adhesions in an ESS sheep model for chronic sinusitis.', 'Prospective, blinded, randomized controlled trial.', 'Sheep (n = 14) with eosinophilic rhinitis (determined by the presence of eosinophilia in nasal secretions) underwent ESS with middle turbinectomies, standardized mucosal injuries created on the lateral nasal wall, and partial thickness wounds created around the ethmoid cell region. Surgery was performed bilaterally (28 nasal cavities). Animals were randomized into treatment with sprayable chitosan/starch-based sealant (n = 7, 14 nasal cavities) or no treatment (n = 7, 14 nasal cavities). Two animals in the treatment group expired due to anesthetic complications associated with the turbinectomies, leaving five animals (10 sites) that completed the study. Presence of adhesions was assessed by endoscopic evaluation at days 14 and 28 after initial surgery. Adhesion formation was confirmed via necropsy of sinus cavities at day 28 after initial surgery.', 'Adhesions were observed in all seven control animals, resulting in an 86% (95% confidence interval [CI], 65-100) adhesion rate (12 of 14 sites). The five surviving treatment animals had a 10% (95% CI, 0-33) adhesion rate (one of 10 sites). Treatment with the sprayable chitosan/starch-based sealant resulted in a 76% reduction (95% CI, 32-100) of adhesions (P < .002).'] Does sprayable chitosan/starch-based sealant reduce adhesion formation in a sheep model for chronic sinusitis?