The prevalence, sex-ratio and clinical characteristics of tension-type headache were analyzed in 4000 people from the general population. The one-year-period prevalence of tension-type headache was not significantly different in people with migraine without aura (83%), in people with migraine with aura (75%) and in people who had never had migraine (76%). The male/female ratio varied from 1:1.19 to 1:1.23 and was not significantly different in the three subgroups. Tension-type headache was significantly more frequent within the last year and lasted longer in migraineurs than in people who had never had migraine. The pain characteristics and accompanying symptoms were very similar in the three subgroups. Tension-type headache was often precipitated by stress, mental tension and tiredness. Only migraineurs had episodes of tension-type headache precipitated by alcohol, over-matured cheese, chocolate and physical activity. We conclude that tension-type headache and migraine are separate disorders and not part of a continuum of headache disorders. However, migraine may aggravate and precipitate tension-type headache possibly due to convergence of various noxious peripheral input into the trigeminal nucleus.