Summary: T-helper 2 (Th2) cell responses play a critical role in protection against helminth infections. In the case of Schistosoma mansoni, an important helminth parasite of man, data from a mouse model of human disease have shown that Th2 responses are essential to allow host survival. In this infection, parasite eggs are the primary stimulus for Th2 response development. Recent work has shown that egg molecules exert multiple levels of control over the development of host interferon-γ-associated inflammatory responses. Soluble egg antigen inhibits the ability of dendritic cells to make interleukin-12 and induces Th2-polarized adaptive immune responses that in combination with regulatory T-cell responses effectively limit Th1 response development. In this article, we discuss the factors influencing Th2 response polarization during infection with S. mansoni.