The concentration of IL-6 and clinical manifestations were investigated in 74 cases of dengue fever (DF) and 30 normal persons as a negative control. Results showed that higher levels of IL-6 in patients with high fever, has significantly compared to the case of low-grade fever with p 0.05. Moreover, in the hemorrhagic group of organs and mucosal bleeding have concentration of IL-6 significantly higher than subcutaneous hemorrhage group with p 0.05. Meanwhile, in patients with dengue-D expression hepatomegaly, high levels of IL-6 increased significantly compared with patients without hepatomegaly with p 0.05. IL-6 is also quite high in the group with both DENV-IgM-IgG compared with DENV-IgM or with DENV-IgG group and DENV-RNA with p 0.05. Therefore, IL-6 is an important biological marker for monitoring, diagnosis, treatment and prognosis of patients with dengue fever.