By planned immunization of a volunteer, two stable (greater than or equal to 6 months), specific, alloreactive cytolytic T-cell clones have been established from his peripheral blood lymphocytes. One clone reacts with all serologically defined HLA-Cw3 cells from our panel, whereas the other defines a split within the serological HLA-B40 specificity. The two cytotoxic clones are SmIg-negative, E-rosette positive, EA and EAC rosette-negative, HLA-A, -B and -C- positive, and also HLA-DR- or 'Ia like'-positive. In addition, they present very similar patterns of iodinated cell surface molecules as analysed by sodium dodecylsulphate polyacrylamide gel electrophoresis (SDS-PAGE), contrasting with that of an EBV cell line derived from the same donor.