A rabbit antibody against the light-chain of guinea-pig high-molecular-weight (HMW) kininogen, which was specific to HWM kininogen and did not recognize low-molecular-weight kininogen, was prepared. This antibody demonstrated the presence of HMW kininogen antigen at the interstitial-tissue space in the guinea-pig skin by means of immunohistochemistry. The interstitial-tissue HMW kininogen antigen was extracted from the skin. This antigen molecule in the skin extract behaved identically as HWM kininogen of plasma in slab-polyacrylamide gel electrophoresis under the presence of sodium dodecyl sulfate followed by immunoblotting. Therefore, it was concluded that HMW kininogen was present in the interstitial-tissue fluid in the skin. The amount of HMW kininogen in the skin extract was quantified by a sandwich enzyme-linked immunosorbent assay with the anti-light-chain antibody and a goat anti-guinea-pig HMW kininogen antibody. On the assumption that the interstitial-tissue volume is 50 ml/100 g wet skin tissue, the average concentration of HMW kininogen in the interstitial-tissue fluid of the skin was calculated to be 23% of the plasma concentration. On the other hand, the proportion of intravascular HMW kininogen (derived from blood remaining in the vessels of the harvested skin) in relation to the total HMW kininogen in the skin extract was quantified by measuring the radio-labelled HMW kininogen which had been injected intravenously as a tracer of the intravascular HMW kininogen. About 5% of the total HMW kininogen in the skin extract was calculated to be derived from the intravascular blood volume of the skin, indicating that the majority of the HMW kininogen in the skin extract was derived from the extravascular-tissue space.