We have generated cDNA expression vectors that efficiently produce tagged proteins. The newly introduced cloning site of this plasmid facilitates subcloning of cDNA in the lambda gt11 phage into the plasmid vector. Because the cDNA is inserted next to the motifs of the tagged DNA sequence, the protein produced by the tag sequence-coupled cDNA is easily detected by Western blot analysis or immunoprecipitation using commercially available antibodies. The double-tagged protein significantly enhances the efficiency of Western blot and immunoprecipitation detection as compared with the single-tagged protein.