Antigen-specific T cell clones are useful reagents for studies of the fine specificity of antigen recognition and of potential therapeutic use in adoptive immunotherapy for human viral and malignant diseases. Culture methods which require antigen and APC for stimulation can be problematic for the generation and long-term growth of human virus and tumor-specific T cells. We have developed an alternative culture method using monoclonal antibodies to T cell activation molecules, CD3 and CD28, as stimulation to efficiently grow CD4+ and CD8+ antigen-specific T cells from single progenitors and expand T cell clones in long-term culture. This method alleviates the requirement for large amounts of viral or tumor antigens and MHC compatible APC to sustain the growth of virus and tumor-specific T cell clones, and, as demonstrated for CD8+ CMV-specific cytotoxic T cells, overcomes the difficulties cloning CD8+ T cells using virally infected cells as antigen-presenting cells. T cell clones generated and maintained with monoclonal antibody stimulation are rapidly expanded and retain antigen-specific responses after 3 months in culture, suggesting this approach may prove useful for growing large numbers of antigen-specific T cell clones for cellular immunotherapy.