Cluster headache (CH) is the commonest of the trigeminal autonomic cephalalgias (TAC) characterized by attacks of severe, strictly unilateral pain, which is orbital, supraorbital, temporal, or in any combination of these sites, with duration of pain attacks of 15 to 180 min. The pain of CH is associated with ipsilateral conjunctival injection, lacrimation, nasal congestion, rhinorrhea, forehead and facial sweating, miosis, ptosis and/or eyelid edema, and/or restlessness or agitation. Headaches often recur at the same time each day during the cluster period, which can last for weeks to months. CH occurs more commonly in male patients (2.5:1 to 4.3:1 male to female) with an average age of onset in the third or fourth decade. The pathophysiology of CH is not fully understood, but may include a genetic component. Treatment focuses on avoiding triggers and includes abortive therapies, prophylaxis during the cluster period, and long-term treatment in patients with chronic CH. Evidence supports the use of supplemental oxygen, sumatriptan, and zolmitriptan for acute treatment of episodic CH. Verapamil is used to treat chronic CH. More invasive treatments, including nerve stimulation and surgery, may be helpful in refractory cases.