The authors developed a phagemid system for monovalent display of combinatorial antibody Fab libraries on the surface of filamentous phage M13. Fab fragments were fused to the C-terminal domain of the gene III (gIII) protein. Phage displaying Fab fragments, or Phabs, were enriched 10² to 10⁵-fold on antigen-coated surfaces over nonspecific phage. This method may replace current antibody cloning techniques. The system allows for the rapid sorting of large combinatorial Fab libraries, which is particularly important for the development of catalytic antibodies. The authors constructed a phagemid vector, pComb 3, that fuses the Fd chain with the C-terminal domain of cpIII, and demonstrated its utility by enriching specific clones from a human antitetanus toxoid Fab library. The monovalent display approach allows for the selection of clones based on both affinity and specificity, mimicking the immune system. This system complements previously reported multivalent display systems and has potential applications in therapy and diagnostics.The authors developed a phagemid system for monovalent display of combinatorial antibody Fab libraries on the surface of filamentous phage M13. Fab fragments were fused to the C-terminal domain of the gene III (gIII) protein. Phage displaying Fab fragments, or Phabs, were enriched 10² to 10⁵-fold on antigen-coated surfaces over nonspecific phage. This method may replace current antibody cloning techniques. The system allows for the rapid sorting of large combinatorial Fab libraries, which is particularly important for the development of catalytic antibodies. The authors constructed a phagemid vector, pComb 3, that fuses the Fd chain with the C-terminal domain of cpIII, and demonstrated its utility by enriching specific clones from a human antitetanus toxoid Fab library. The monovalent display approach allows for the selection of clones based on both affinity and specificity, mimicking the immune system. This system complements previously reported multivalent display systems and has potential applications in therapy and diagnostics.