We measured CD8 T cell clonotypic diversity to three epitopes recognized in C57BL/6 mice infected with mouse hepatitis virus, strain JHM, or lymphocytic choriomeningitis virus. We isolated epitope-specific T cells with an IFN-γ capture assay or MHC class I/peptide tetramers and identified different clonotypes by Vβ chain sequence analysis. In agreement with our previous results, the number of different clonotypes responding to all three epitopes fit a log-series distribution. From these distributions, we estimated that> 1000 different clonotypes responded to each immunodominant CD8 T cell epitope; the response to a subdominant CD8 T cell epitope was modestly less diverse. These results suggest that T cell response diversity is greater by 1–2 orders of magnitude than predicted previously.