Kunitz-type soybean trypsin inhibitor (SBTI) and chondroitin sulfate (A, and C type) were conjugated using sodium periodate method. And the physicochemical, pharmacokinetic properties and immunogenecity of the conjugates (Chon-A-SBTI or Chon-C-SBTI) were characterized. We expected the conjugation using chondroitin sulfate to reduce the immunogenecity and to improve the pharmacological effect. As the results, the mean molecular weight of the conjugate highly increased. After I.V. injection of the radiolabeled conjugates or native SBTI into mice, it was found that native SBTI showed rapid elimination from plasma, whereas Chon-A-SBTI and Chon-C-SBTI were slowly eliminated. Organ distribution of the two agents at 30 min after I.V. injection was different : Chon-A-SBTI or Chon-C-SBTI accumulated to a large extent in the liver (13% in Chon-A-SBTI and 16% in Chon-C-SBTI), whereas native SBTI was taken up more rapidly by the kidney (107% dose/g of tissue) and excreated into the urine (26%). In addition we evaluated the therapeutic value of the conjugates by using the sublethal septic shock model caused by pseudomonal elastase and tested the immunogenecity by passive cutaneous anaphylaxis shock (PCA). The conjugates were more effective than native SBTI against pseudomonal elastase induced septic shock in guinea pig. In case of the conjugates, the pharmacological and therapeutic effect lasted over 3 hours long. In immunogenecity test, both of the conjugates showed the reduction of their immunogenecity, especially Chon-A-SBTI looked most effective.