The International Headache Society (I.H.S.) classification system for chronic tension-type headache requires the following:

1. At least 15 headache days/month for 6 months fulfilling the criteria in B and C
2. At least two of the following:
1. Pressing/tightly (non-pulsating) quality
2. Mild or moderate activity (i.e. not severe - incapacitating)
3. Bilateral location
4. No aggravation by walking stairs or similar routine physical activity
3. Both of the following:
1. No vomiting
2. Only one of Photophobia (light is uncomfortable), Phonophobia (noise is uncomfortable), or nausea is present