Medication-overuse headache (MOH) has developed into the third most common type of headache after tension-type headache and migraine. The prevalence reaches approximately 1% of the world's population and shows an increasing trend. Many important studies on MOH have been published in the last year, some of which investigated the pathophysiology of headache chronicity, with others focusing on the evaluation of risk factors. The International Headache Society revised its classification criteria on MOH. Several large population-based longitudinal studies clearly demonstrated that overuse of any kind of acute headache medication is the main risk factor leading to the development of chronic headache. Management of MOH remains difficult; the only effective treatment concept is consequent withdrawal therapy.