This chapter seeks to familiarize the readers with the assessment of unconscious patient. Coma is a state of unconsciousness caused by temporary or permanent impairment of the ascending reticular system in the brainstem, or both cerebral hemispheres. Breathing pattern is often forgotten in intubated patients, but is important as the pattern of breathing correlates with the level of the lesion, and may suggest other causes. Most individuals have a degree of exophoria when drowsy for any reason and any underlying strabismus tends to worsen, thus dysconjugate gaze is difficult to interpret in the stupor or comatose patient. Patients that chronically wear contact lenses may have diminished corneal reflexes. Gag and cough reflexes, motor responses, signs of the underlying cause, and fundoscopy are also covered thoroughly in this chapter.