The natural history of untreated HIV-1 infection is characterized by progressive erosion of the immune system with eventual loss of viral control. T helper cell responses to HIV-1 are typically weak or absent in chronically HIV-1 infected individuals. CD4⁺ T helper cell responses have been shown to be important in a number of experimental viral infection systems, and here we explore the ways in which T helper cells might aid in the control of viruses in general and HIV-1 in particular. We first review the relationship between T helper cells and other arms of the immune system. We then focus on the role T helper cells play in viral control in murine and nonhuman primate models, and finally review what is known of CD4⁺ T helper cell function in HIV-1 infection.