Murine cytolytic T lymphocytes (CTL) clones were solubilized in Nonidet P-40 detergent, and the matrix and membrane proteins separated from the nuclear constituents. These proteins, in combination with exogenous lipids and Sendai virus envelope proteins, were used to construct liposomes that were then fused with noncytolytic cloned T cell recipients. The resultant fusion products were found to be highly cytolytic and appeared to express the same specificity as the original donor clone. Further analysis showed that the liposomal transfer process was extremely efficient. Moreover, in addition to noncytolytic T cell clones, three transformed T cell lines and one B cell line were found to express specific cytolytic activity after fusion with appropriate liposomes. Inhibition experiments using monoclonal antibodies against target cell antigens, as well as analysis of the lytic reactivity pattern of the fusion products, confirmed the high degree of specificity conferred to the recipient cells. This study thus indicates that the two characteristics typically associated with CTL, namely antigen-specific recognition and cytolytic activity, can be solubilized from CTL and transferred to recipient cells that do not express these characteristics.