Over the last 10 years an increasing amount of data regarding the prevalence of chronic daily headache (CDH) has been published. The economic implications of chronic daily headache have now grown in importance in view of the increasingly limited financial resources in the health care system. In addition to recording data regarding the prevalence of this disease, epidemiological studies have also dealt with analysing and evaluating the quality of life of the afflicted patients. According to population-based data from the USA, Europe and Asia, approx. 4-5% of the population suffer from chronic daily headache. These have been equated up until now with chronic tension-type headache (CTTH). More recent epidemiological studies have resulted in an adaptation of this point of view. Currently it is assumed that approx. 2-3% of the population suffer CTTH, which preferably affects females (approximately twice as frequently); approx. 2 % suffer chronic migraine (transformed migraine = TM) and 0.2 % are afflicted with a so-called new daily persistent headache or very rarely a hemicrania continua.