Dengue virus infections are a serious public health problem in tropical and subtropical areas of the world. Based on epidemiological data, it has been postulated that immune responses to dengue virus contribute to the pathogenesis of severe dengue illness, dengue hemorrhagic fever (DHF) and dengue shock syndrome (DSS). Host immune responses are also important for controlling dengue virus infection. Therefore, dengue virus infections are an interesting model to explore the interactions between viruses and the immune system which result in immunopathology or recovery from infection. In this paper, we review immune responses to dengue viruses with an emphasis on the human T cell responses, and discuss possible roles of these immune responses in the control of dengue virus infection and in the pathogenesis of DHF/DSS.