BACKGROUND: The purpose of this research is to verify through a blind, controlled study if there is a positive correlation between tension-type headache and the most likely causative factors. In accordance with the headache classification of the international headache society, they are: oro-mandibular dysfunction; psychosocial stress; anxiety; depression; headache as a delusion or an idea; muscular stress; drug overuse for tension-type headaches. METHODS: The subjects who participated in the study were selected from patients diagnosed as having tension-type headache. The patients were of both sexes and aged between 18 and 60 years. A control subject was joined to every case. 102 subjects entered the study. The protocol includes the following examinations: questionnaire about the headache's characteristics; questionnaire about muscular stress; questionnaire about sleep; physiologic and pathologic history; structured Clinical Interview for DSMIII-R (Diagnostic and Statistical Manual of Mental Disorders) for diagnosis of anxiety, depression and somatoform disorder; DSMIII-R questionnaire about psychosocial stressors; EMG; algometry; evaluation of the TMJ; evaluation of the muscles of mastication; evaluation of the denture. RESULTS AND CONCLUSIONS: A positive correlations between oro-mandibular dysfunction, anxiety, muscular stress and tension-type headache was found.