Medication Overuse Headache (MOH) is an illness affecting about 1,5 % of the general population. It is characterized by chronic headache occurring for at least 15 days a month, by a use of antimigraine drugs during at least 3 months for more than 10 days a month (for ergots, triptans, opiate derivates and combined analgesics) or for more than 15 days a month (for simple analgesics). The chronic headache must have occurred during the period of antimigraine drug abuse and the headache must have returned to its episodical pattern after withdrawal of antimigraine drugs. But, about 50% of the MOH patients will relapse during the first year following the antimigraine drugs withdrawal.