At the end of the T cell response, the majority of the activated T cells die. We activated Vβ8⁺ T cells with staphylococcal enterotoxin B (SEB) in vivo and monitored the expansion and deletion of Vβ8⁺ T cells. We found that, in response to SEB, activated T cells died in vivo in the absence of Fas or TNF-R signaling but not when they overexpressed human Bcl-2. We also found that Vβ8⁺ T cells from Bim-deficient mice are resistant to SEB-induced deletion. While Bim levels did not change, endogenous Bcl-2 levels within Vβ8⁺ T cells decrease following SEB injection. Thus, the death of superantigen-stimulated T cells in vivo is mediated by Bim and may be modulated by a decrease in Bcl-2.