Tension-type headache is the most prevalent type of primary headache but is frequently forgotten by the patient and doctor. This article summarizes the present knowledge about tension-type headache and discusses some of the problematic aspects. Most patients in specialized headache clinics suffer from several different primary and secondary headaches at the same time and deserve a careful characterization before a rational therapy can be initiated. In particular, it is of utmost importance to increase focus on clinical and basic research in order to develop effective treatment strategies for the most neglected and most costly type of headache.