Herpesvirus saimiri (EIVS) was used to infect and transform human CD8+ cytotoxic T lymphocytes (CTL), and the phenotypic and functional consequences of HVS infection of CD8+ T lymphocytes were investigated. HVS-transformed CTL no longer require antigen restimulation yet maintain their phenotype and HLArestricted cytolytic function and specificity. The ability of HVS to transform CTL may have an important role in the functional analysis of human antigen-specific CTL.