ABSTRACT.Purpose: To compare emedastine ophthalmic solution 0.05% BID to levocabastine ophthalmic suspension 0.05% BID in reducing chemosis, eyelid swelling and other signs and symptoms in subjects with seasonal allergic conjunctivitis. Methods: In a randomized, double-masked, parallel controlled study, emedastine ophthalmic solution 0.05% BID was compared to levocabastine ophthalmic suspension 0.05% BID for control of chemosis, eyelid swelling and other parameters in the environmental allergy study model. Results: At Days 7, 14, 30 and 42, emedastine was significantly better than levocabastine at controlling chemosis and eyelid swelling (p∞0.05). A statistical trend was seen at Day 3 (0.05∞p∞0.10). Results were clinically relevant at Days 30 and 42. Emedastine was also significantly better at reducing redness and itching at Days 7, 14, 30 and 42 (p∞0.05). Conclusion: Emedastine is more efficacious than levocabastine in reducing chemosis, eyelid swelling and other efficacy variables associated with seasonal allergic conjunctivitis.