CTLs are important mediators of pancreatic β cell destruction in the nonobese diabetic mouse model of type 1 diabetes. Cross-presentation of Ag is one means of priming CTLs. The death of Ag-bearing cells has been implicated in facilitating this mode of priming. The role of β cell death in facilitating the onset of spontaneous autoimmune diabetes is unknown. Here, we used an adoptive transfer system to determine the time course of islet-derived Ag presentation to naive β cell-specific CD8 T cells in nonobese diabetic mice and to test the hypothesis that β cell death enhances the presentation of β cell autoantigen. We have determined that β cell death enhances autoantigen presentation. Priming of diabetogenic CD8 T cells in the pancreatic lymph nodes was negligible before 4 wk, progressively increased until 8 wk of age, and was not influenced by gender. Administration of multiple low doses of the β cell toxin streptozotocin augmented in situ β cell apoptosis and accelerated the onset and magnitude of autoantigen presentation to naive CD8 T cells. Increasing doses of streptozotocin resulted in both increased pancreatic β cell death and significantly enhanced T cell priming. These results indicate that in situ β cell death facilitates autoantigen-specific CD8 T cell priming and can contribute to both the initiation and the ongoing amplification of an autoimmune response.