For the primary care physician, the occurrence of a red eye is a frequent and prominent finding of a disease process in patients. A careful history and simple examination with the observation of typical clinical signs are important for the management of this common disorder. The causes can be classified as painful red eye, trauma, and other common conditions. The most frequent causes of a red eye, such as dry eye, conjunctivitis, keratitis, iritis, acute glaucoma, subconjunctival hematoma, foreign bodies, corneal abrasion, and blunt or penetrating trauma, are described in this article. Simple diagnostic methods and an emergency management with some useful topical ophthalmic preparations are included. Although several conditions can be treated by the primary care physician the clinical signs that require an urgent ophthalmic consultation are chemical burns, intraocular infections, globe ruptures or perforations, and acute glaucoma.