The dynamics of mouse cytomegalovirus (MCMV)-specific CD4 T cell responses and the mechanisms by which these cells contribute to viral control are not well understood, mainly due to lack of appropriate tools to characterize MCMV-specific CD4 T cells. We therefore generated MCMV-specific CD4 T cell hybridomas, then used an MCMV expression library and overlapping peptides to identify CD4 T cell epitopes. We used these novel tools to study the long-term kinetics and organ distribution of MCMV-specific CD4 T cells in comparison to MCMV-specific CD8 T cell responses. We demonstrate that the overall MCMV-specific CD4 T cell response stabilizes during the latent stage, which stands in contrast to subpopulations of MCMV-specific CD8 T cells and HCMV-specific CD4 T cells which accumulate over the course of CMV latency. Furthermore, MCMV-specific CD4 T cells displayed a Th1 phenotype, secreting high levels of IFN-gamma and TNF-alpha and to some extent IL-2, cytokines which are involved in protection from CMV disease.