Objective To study the changes in the serum interleukin 8(IL-8) levels in patients with tension-type headache (TTH) and its clinical significance,Meteods 60 patients with TTH were selected and treated with Tianshu Capsule for eight weeks (TTH group);the levels of peripheral blood (PB) IL-8 and 5-hydroxytryptamine (5-HT) and the visual analogue scale (VAS) scores before and after the treatment were detected by use of ELISA method.A contrast analysis was conducted on the results and those in the control group (constituted by 60 healthy persons).Results Before the treatment,the serum IL-8 levels and VAS scores were significantly higher than those in the control group (P < 0.01),while the serum 5-HT levels was much lower than that in the control group (P < 0.01).Compared with those before the treatment,the post-treatment serum IL-8 levels and VAS scores in TTH group decreased significantly (P < 0.01),while the serum 5-HT levels increased significantly (P < 0.01).The serum 5-HT levels were in significant negative correlation with VAS scores in TTH group(r=-0.736,P < 0.01),while IL-8 levels were in positive correlation with VAS scores (r=0.742,P < 0.01).Conclusion The serum IL-8 and 5-HT levels in patients with TTH are correlated with the pain degree,which may be used as an indirect index for evaluating the severity of TTH.