Cluster headache is a stereotypic headache disorder marked by short-lasting bouts of severe unilateral head pain and associated autonomic symptoms. Almost pathognomonic of this condition are nocturnal attacks that usually occur during the first random eye movement sleep phase of the evening. Melatonin levels have been found to be decreased in cluster headache patients. A lack of melatonin secretion may predispose the cluster sufferer to nocturnal and, possibly, daytime attacks. Leone et al. demonstrated that melatonin could rapidly alleviate cluster attacks, but only in episodic cluster patients. We report two chronic cluster headache patients who had both daytime and nocturnal attacks that were alleviated with melatonin.