OBJECTIVE To examine the prevalence, impact, and related medication use or overuse of primary chronic daily headache (CDH) among adolescents in a field sample. METHODS The authors conducted a two-phase CDH survey of all students from ages 12 to 14 years in five selected middle schools in Taiwan. Subjects with CDH in the past year were identified and interviewed by neurologists. CDH was defined as headache occurring at a frequency of 15 days/month or more, average of 2 hours/day or more, for more than 3 months, and its subtypes were classified on the basis of the International Classification of Headache Disorders, 2nd edition. RESULTS Of the 7,900 participants, 122 (1.5%) fulfilled the criteria for primary CDH in the past year. Girls had a higher prevalence (2.4%) than boys (0.8%) (p < 0.001). Of the CDH subjects, 88 (72%) could be classified into either chronic tension-type headache (65.6%) or chronic migraine (6.6%). None of them fulfilled the criteria of new daily-persistent headache or hemicrania continua. Twenty-four subjects (20%) overused medications. Eighty-two (67%) of all CDH subjects had migraine or probable migraine. In the past semester, most CDH subjects (65%) did not take any sick leave for headaches. Only 6 subjects consulted neurologists in the past year, and only 1 subject took headache prophylactic agents. CONCLUSIONS Chronic daily headache (CDH) was common in a large nonreferred adolescent sample. Based on the International Classification of Headache Disorders, 2nd edition, criteria, chronic tension-type headache was the most common subtype; however, a majority of adolescents with CDH had headaches with features of migraine.