The prevalence of oromandibular dysfunction was studied in 735 subjects from a random sample population of 1,000 subjects aged 25 to 64 years. A diagnosis of oromandibular dysfunction was based on criteria established by the International Headache Society, as a subgroup to tension-type headache. Tenderness in pericranial or jaw muscles was not included. The most common symptoms were clenching (22%) and grinding of teeth (15%). The most common sign was irregular jaw movements on opening and closing (29%). The ratio of men to women for most symptoms and signs ranged from 2:3 to 1:3. This study serves as a base in evaluating the importance of oromandibular dysfunction as a causative factor for tension-type headache.