Cytomegalovirus (CMV) belongs to the Betaherpesvirinae subfamily of Herpesviridae viruses. A primary CMV infection, which usually occurs in childhood, is asymptomatic in immunocompetent individuals. Usually, following the primary infection, the virus cannot be fully eliminated from the host, thus resulting in latent infection of the host’s tissues, mainly in myeloid precursor cells. Although such latently infected CMV seldom causes severe infectious disease in an immunocompetent state, it does provoke various types of inflammatory diseases, such as pneumonitis, retinitis, gastritis, and colitis, in immunosuppressed patients. It has been recently reported that latent infection and the reactivation process of CMV are closely associated with the differentiation state of immature precursor cells and chromatin remodeling of the latently infected cells. Considering that symptomatic CMV diseases are observed in such immunosuppressed patients as transplant and AIDS patients, it is true that the host’s immunity must have a crucial role in the pathogenesis of CMV. In addition, some gene products derived from human CMV act to induce immune evasion of the virus from the host’s CD8 T cells. Therefore, immunity is closely related to the pathogenesis and regulation of CMV. In this review article, the relationship between CMV and immunity is discussed using the research results of our group and addressing other related published manuscripts.