Cluster headache is a distinctive syndrome, also known as migrainous neuralgia. There are two main clinical patterns of cluster headache – episodic cluster headache and chronic cluster heachache. Episodic is the most common pattern and is characterized by 1-3 short attacks of pain around the eyes per day, with these attacks clustered over a stretch of 1-2 months followed by a pain-free remission. The average length of remission is a year. Chronic is characterized by the absence of sustained periods of remission. Chronic cluster headache may start with no past history of cluster headaches, or it may emerge several years after the patient has experienced an episodic pattern of cluster headaches. The episodic and acute forms of cluster headache may transform into one another, so it seems most likely that they are merely different-appearing clinical patterns of one and the same disease. Although the mechanisms underlying cluster headache and migraine may have a degree of commonality, cluster headache looks to be different and distinct as a disease from migraine. For example, propranolol is effective for migraine but not cluster headache while lithium benefits cluster headache syndrome but not migraine.