||BACKGROUND AND PURPOSE: During the past decade, several population-based studies have found an inverse association between blood pressure (BP) and headache. However, most of them have a cross-sectional design or lack a validated definition of a headache-free population at baseline. Therefore, additional population-based studies using a clearly defined headache-free population and a prospective design are warranted. METHODS: Data from two large epidemiological studies, the Nord-Trondelag Health Survey 1995-1997 (HUNT 2) and 2006-2008 (HUNT 3), were used to evaluate the association between BP (systolic, diastolic and pulse pressure) at baseline and headache (migraine and tension type headache) at follow-up. RESULTS: An inverse relationship was found between all three BP measures at baseline in HUNT 2 and any headache in HUNT 3, more evident for systolic BP [odds ratio (OR) 0.90 per 10 mmHg increase in systolic BP, 95% confidence interval (CI) 0.87-0.93, P < 0.001] and pulse pressure (OR 0.84 per 10 mmHg increase in pulse pressure, 95% CI 0.80-0.89, P < 0.001) than for diastolic BP (OR 0.92 per 10 mmHg increase in diastolic BP, 95% CI 0.87-1.00, P = 0.036). The most robust finding, evident for both sexes, was that increased pulse pressure was linked to decreased prevalence of both migraine and tension type headache. CONCLUSION: An inverse relationship between BP and subsequent development of headache was confirmed in this large-scale population-based cohort study. Nevertheless, further research is needed to investigate the underlying mechanisms explaining these findings.