It is generally accepted that virus-specific CD8+ cytotoxic T lymphocytes (CTLs) recognize nine-amino acid peptides in conjunction with HLA class I molecules. We recently reported that dengue virus-specific CD8+ CTLs of two different serotype specificities, which were established by stimulation with dengue virus, recognize a single nine-amino acid peptide of the nonstructural protein NS3 of dengue virus type 4 (D4V) in an HLA-B35-restricted fashion. To further analyze the relationships between the serotype specificities of T cells and the amino acid sequence of the recognized peptides, we examined the ability of this viral peptide D4.NS3.500-508 (TPEGIIPTL) to stimulate T lymphocytes of an HLA-B35-positive, dengue virus type 4-immune donor. Peptide stimulation of the PBMC generated dengue virus-specific, HLA-B-35-restricted CD8+ CTL clones. These clones lysed dengue virus-infected autologous cells, as well as autologous target cells pulsed with this peptide. Four patterns of dengue virus serotype specificities were demonstrated on target cells infected with dengue-vaccinia recombinant viruses or pulsed with synthetic peptides corresponding to amino acid sequences of four dengue virus serotypes. Two serotype-specific clones recognized only D4V. Three dengue virus subcomplex-specific clones recognized D1V, D3V, and D4V, and one subcomplex-specific clone recognized D2V and D4V. Three dengue virus serotype-cross-reactive clones recognized D1V-D4V. Thus, a single nine-amino acid peptide induces proliferation of a heterogeneous panel of dengue virus-specific CD8+ CTL clones that are all restricted by HLA-B35 but have a variety of serotype specificities. Peptides that contain a single amino acid substitution at each position of D4.NS3.500-508 were recognized differently by the T cell clones. These results indicate that a single epitope can be recognized by multiple CD8+ CTLs that have a variety of serotype specificities, but the manner of recognition by these multiple CTLs is heterogeneous.