From a panel of monoclonal antibodies of dengue viruses, a serotype-specific epitope of dengue virus 1 was screened from a random peptide library displayed on phage. The epitope was the determinant reactive with monoclonal antibody 15F3-1 that was specific to dengue 1. The screening was monitored by a dot blotting procedure, and after three rounds of screening a consensus motif, HRYSWK, was found. This sequence matches the sequence HKYSWK, corresponding to the amino acid residues 885-890 of polyprotein or residues 111-116 of the non-structural protein 1 of dengue virus serotype 1. The linear epitope was confirmed by testing the antigenicity of chemically synthesized 8-branched peptide.