Leukotriene C(4) (LTC(4)) is synthesized by binding of glutathione to LTA(4), an epoxide derived from arachidonic acid, and further metabolized to LTD(4) and LTE(4). We previously prepared a monoclonal antibody with a high affinity and specificity to LTC(4). To explore the structure of the antigen-binding site of a monoclonal antibody against LTC(4) (mAbLTC), we isolated full-length cDNAs for heavy and light chains of mAbLTC. The heavy and light chains consisted of 461 and 238 amino acids including a signal peptide with molecular weights of 51,089 and 26,340, respectively. An expression plasmid encoding a single-chain antibody comprising variable regions of mAbLTC heavy and light chains (scFvLTC) was constructed and expressed in COS-7 cells. The recombinant scFvLTC showed a high affinity with LTC(4) comparable to mAbLTC. The scFvLTC also bound to LTD(4) and LTE(4) with 48% and 17% reactivities, respectively, as compared with LTC(4) binding, whereas the antibody showed almost no affinity for LTB(4).