Ever since cluster headache was recognized as a clinical picture, there has been a dispute as to its correct position in the classification of clinical headaches. In early years, many workers in the field seemed to opine that cluster headache belongs to the "vascular headaches of the migraine type". As years went by, more and more investigators seem to have changed their mind and viewed cluster headache as a disorder that differs from migraine.There are many features that distinguish cluster headache and migraine. First of all, the clinical pictures of the two headaches are clearly at variance: familial incidence of similar (or identical) headache; duration of headache attacks; sex preponderance; unilaterality; the presence of the cluster phenomenon per se; and the presence of accompanying phenomena. Taking into consideration the fact that there are not an abundance of ways in which headaches can manifest themselves, these differences are no less than impressive.Moreover, there are clear differences in the treatment profiles, and there are drugs with a rather selective action in the two headaches. Thus, beta-blocking agents are helpful in migraine but have not, so far at least, found any place in the treatment regimen of cluster headache. Conversely, some drugs are effective in cluster headache but not in migraine. Oxygen seems to belong to this category of "drugs". Lithium even seems to exert a contrary effect in migraine (1). A few drugs are of benefit in both types of headaches, like ergotamine, methysergide, and pizotifen, probably because their headache-abating effect is non-specific.The prognoses also seem to differ clearly.