The red eye is a clinical problem encountered on a daily basis in most emergency departments. A careful history and focused ophthalmologic examination will lead to a correct diagnosis and proper therapy. The red eye without photophobia, pain, or visual disturbance is most commonly a result of conjunctivitis. The presence of any of these symptoms indicates a need to investigate for a more serious cause. Infectious causes of conjunctivitis should always be investigated, but allergies and hypersensitivity also should be considered if the history is appropriate. Emergency department treatment of the red eye should only include corticosteroids when the diagnosis is certain and ophthalmologic consultation is obtained.