Cytomegalovirus (CMV) is a widely prevalent herpesvirus and establishes persistent infection. Viral replication is controlled by sustained immune pressure that permanently alters the host immune repertoire. CMV is an important pathogen and optimisation of immune control has the potential to improve a range of health outcomes. Furthermore, insights into how the immune system can effectively control a chronic antigenic challenge such as CMV has implications for other disorders such as cancer. The talk will review current understanding of cellular immunity to herpesviruses and provide insights into future directions of research.