The external eye is one of the most vulnerable parts of the body exposed to the outside world. Problems of the ocular surface are diverse with respect to etiology, symptoms, and prognosis. They range from relatively minor irritations to potentially blinding conditions. This course is adapted from material in the current edition of the Basic and Clinical Science Course and provides an overview of recent developments in the anatomy and physiology of the ocular surface and discussions of the more common or serious disorders affecting the surface of the conjunctiva and cornea.