The aim of this study was to investigate the association between caffeine consumption and headache type and frequency in the general adult population. The results were based on cross-sectional data from 50,483 (55%) out of 92,566 invited inhabitants aged >or=20 years who participated in the Nord-Trøndelag Health Survey. In the multivariate analyses, adjusting for age, gender, smoking, and level of education as confounding factors, a weak but significant association (OR = 1.16, 95% CI 1.09-1.23) was found between high caffeine consumption and prevalence of infrequent headache. In contrast, headache >14 days/month was less likely among individuals with high caffeine consumption compared to those with low caffeine consumption. The results may indicate that high caffeine consumption changes chronic headache into infrequent headache due to the analgesic properties of caffeine. Alternatively, chronic headache sufferers tend to avoid intake of caffeine to not aggravate their headaches, whereas individuals with infrequent headache are less aware that high caffeine use can be a cause.