Tension - type headache is one of the widely spread types of idiopathic headaches. The pathogenesis of the disease includes depression and change in brain serotonin level. The aim of the research is to study the characteristics of ache and the level of serotonin in blood serum in tension-type headache. The intensity of ache, complex psychometric parameters and the level of serotonin in blood serum were investigated in 100 patients (75% females and 25% males from 17 to 55 years old) with tension-type headache. The average period of the illness was 6-5 years. The diagnosis has been determined according to MKGB (2003) criteria. According to the duration of anamnesis of ache the patients were divided into 3 groups: the first - 66 patients, the second - 24 patients, the third - 10 patients with tension-type headache and migraine. Ache status and its impact on different spheres of activity were assessed according to international 150 millimeters visual analogous scale. The research showed that all patients with tension-type headache had moderate ache syndrome, depression and anxiety of the middle or high rate which were in inverse dependence on serotonin rate in the blood. Intensity of episodic tension-type headache (n=24) was 52 mm according to visual analogous scale, the high rate of anxiety (51,08+/-4,2 scores), moderate rate of depression (12,9 scores according to Bek scale) and tendency of serotonin decreasing in blood (205,72+/-6,74 ng ml) was noted. The research of 76 patients with chronic tension-type headache with cephalgy intensity according to VASH 62 mm the high indicators of reactive (46,81+/-2,68 scores) and personal anxiety, the rate of depression (22,4+/-1,64 according to Bek scale) were associated with the displayed decreasing of serotonin amount in blood (119,38+/-9,42 ng/ml). It was concluded that, tension-type headache and moderate ache syndrome leads to depression decreased self-control of pain and life quality. The quality of serotonin in blood decreases in patients with tension-type headache. The relationship between the intensity of pain syndrome, decrease of work capacity, life quality, and quantity of serotonin in patients with ageing was revealed. It is concluded that serotonin level in blood serum may be considered as pain intensity, degree of depression and index of efficacy of depression treatment. Serotonin is an extremely important neurohormone and its metabolism further study will show new characteristic features of its activity in cerebral neurochemical processes. Scientists thought, that the increased activity caused the psychological disorder, changes in the mood and depression. But the results of the last studies show that the person with the abnormal activity of serotonin does not realize the sense of danger and accordingly the main instinct of self-preservation is broken.