The objective was to compare the Severity of Dependence Scale (SDS) score and pattern of medication use in persons with secondary chronic headache (>or= 15 days/month for at least 3 months) in a cross-sectional epidemiological survey. A posted questionnaire screened for chronic headache. Neurological residents interviewed those with self-reported chronic headache. The International Classification of Headache Disorders was used. Split file methodology was employed for data analysis. People with secondary chronic headaches were identified in an age and gender stratified sample of 30,000 30-44 year olds from the general population. The interviews and examinations were conducted at the Akershus University Hospital, Oslo, Norway. The main outcome measure was the SDS score in those with and without medication overuse. Fifty-five (49%) of the 113 persons with secondary chronic headaches were found to have medication overuse. Fifty-eight percent overused simple analgesics and 31% overused combination analgesics. The SDS score was significantly higher among those with than without medication overuse (5.5 vs. 1.9). The sensitivity, specificity, positive and negative predictive values were 0.82, 0.82, 0.82 and 0.83, respectively. Thus the SDS score correlates with medication overuse, and a high SDS score suggests dependency-like behaviour in persons with secondary chronic headache. The use of SDS score in subjects with frequent pain episodes may contribute to the detection of medication overuse and better management of this group of patients.