Abstract: Filamentous bacteriophages are particularly efficient for the expression and display of combinatorial random peptides. Two phage proteins are often employed for peptide display: the infectivity protein, pIII and the major coat protein, pVIII. The use of pVIII typically requires the expression of two pVIII genes: the wild type and the recombinant pVIII genes to generate mosaic phages. “Type 88” vectors contain two pVIII genes in one phage genome. A novel “type 88” expression vector has been rationally designed and constructed, which can be used to express recombinant peptides as pVIII chimeric proteins in mosaic bacteriophages. This vector is not only genetically stable but also of high copy number and produces high titers of recombinant phages.