A strategy based on polymerase chain reaction (PCR) and a phagedisplay system for the rapid method for constructing and screening functional single chain antibody genes was reported. Total RNA from a hybridoma (C50) producing an antibody that reacts with carcinoembryonic antigen (CEA) was used as a template to make the first strand of a cDNA, lightand heavy-chain variable-region genes were separately amplified by PCR. Then whole single chain antibody gene was synthesized and amplified by using two sets of DNA primers that(1) hybridized to the ends of the light- and heavy-chain variable regions, ( 2 ) encoded a Linker peptide, and(3)contained appropriate restriction enzyme sites for cloning. After 30 cycles of PCR, the DNA fragments containing sequences encoding the light- and heavy-chain variable regions were cloned into pCANTAB 5 phagemid containing gene Ⅲ of the phage. Clones encoding single-chain antibody was express on the surface of the phage as a fusion with gene Ⅲ protein. Recombinant phage expressing anti-CEA single chain antibody which retained its antigen-binding capability was screened by affinity selection and enriched. By using this approach it should be possible to rapidly clone and screen the functional variable region sequences of many different antibodies from hybridoma RNA.