Human cytotoxic T cells (Tc) specific for autologous adult T cell leukemia virus- (ATLV) bearing cells were induced in vitro. Peripheral blood leukocytes (PBL) from healthy donors were stimulated repeatedly with autologous ATLV-bearing T cells. In two out of four seropositive donors and one out of two seronegative donors, the responder cells showed cytotoxicity for autologous ATLV-bearing cells, but not for autologous PBL, autologous cloned T cell lines, Epstein Barr virus-transformed autologous lymphoblastoid B cell line (LCL) cells, or various ATLV-negative cell line cells. The effector cells induced were cytotoxic T cells possessing Leu-1 and Leu-2a antigens that were able to proliferate continuously in vitro with periodic restimulation by appropriate cells and supplementation with partially purified T cell growth factor (TCGF). Of three Tc lines tested, one exhibited significant cytotoxicity against allogeneic ATLV-bearing cells that shared HLA-A2 antigen with the effector cells, possibly indicating HLA-restriction of ATLV-specific Tc. HLA-restriction was also suggested by cold target inhibition of cytotoxicity. Interestingly, Tc from this individual could also kill fresh adult T cell leukemia cells that were not expressing the ATLV surface antigens. These results, together with the target specificities of other Tc lines, suggest the possibility of at least two distinct target antigens recognized by ATLV-specific Tc, with one of these antigens differing from the ones detected by serologic methods.