Human kappa-light chains (L chains) were amplified by the reverse transcriptase-polymerase chain reaction (PCR) and cloned into a phagemid vector. Phage particles displaying L chains were fractionated on immobilized vasoactive intestinal peptide (VIP). The resultant phage preparation displayed saturable binding of (tyr(10)-I-125)VIP. One of the L-chain clones (hk13) was deduced to be related to subgroup I of kappa-light chains based on its nucleotide sequence. The VIP binding activity of the soluble and phage-displayed form of this L chain was confirmed by radioimmunoassay and ELISA, respectively. These observations demonstrate the potential of selecting antigen-specific L chains from phage-display libraries.