Earlier reports regarding secular trends of migraine are conflicting, and there is a lack of long-term follow-up studies of other headache syndromes among adults. The aim of the present study was to assess any changes in the prevalence of the major headache types in a large adult population. With an 11-year interval, all inhabitants aged =20 years (n?=?92,566 and 94,194) in the Norwegian county of Nord-Trøndelag were invited to participate in two cross-sectional surveys. Attendance rates were 56% and 42%. The age-adjusted 1-year prevalences, according to the diagnostic criteria of the International Headache Society, sex-ratios and attack frequencies were assessed. The migraine prevalence increased from 12.1% to 13.2% (P?