Tension-type headache (TTH) is a very common problem that usually causes only minimal to moderate discomfort and little disability. If episodic TTH evolves to chronic TTH, then the morbidity in terms of discomfort, disability, and use of medication escalates dramatically. There are no long-term studies, but inferences can be made from population surveys. These suggest that episodic TTH occurs in 15% to 75% of the population, but 30% to 40% is the most common estimate. There is a modest increase in prevalence between the ages of 30 and 50 years and a decrease to 25% to 35% prevalence after the age of 60 years. TTH appears to remain a problem for most sufferers throughout their lives.