This chapter discusses headache and facial pain, where headaches and facial pains can be grouped into primary, secondary, and other. Primary headaches include such entities as migraine, tension-type headache and cluster headache. Secondary headaches are those for which specific causative factors can be demonstrated such as trauma, vascular disorders, infection, substances and those attributed to disorders of the cranium, eyes, ears, nose, sinuses, teeth, mouth, or other facial structures. A recently-defined category consists of disturbances of homeostasis and psychiatric disorders. Sleep apnea induced headache requires polysomnographic documentation of a respiratory disturbance index of more than 5. Headaches can be classified by the extent of associated disability as mild, moderate, and severe. Headache might be an indicator of eye problems and anyone suffering from constant headache should consult an ophthalmologist.