A specific plasma kallikrein inhibitor, Bz-Pro-Phe-boroArg (P8720), was used to define the relationship between the kallikrein-kinin (K-K) system and acute intestinal inflammation induced by bacterial peptidoglycan-polysaccharide (PG-APS) in Lewis rats. Group I received human serum albumin (HSA) intramurally in the intestine and was treated with HSA. Group II received PG-APS and was treated with P8720. Group III received PG-APS and was treated with HSA. P8720 attenuated the decrease of high-molecular-weight kininogen and factor XI activity (group II vs group III, P < 0.01). P8720 therapy significantly but modestly decreased acute intestinal inflammation measured by gross gut score (P < 0.01) and more dramatically reduced the tissue myeloperoxidase activity (P < 0.05), a measure of granulocyte recruitment, in group II compared with group III. We conclude that the K-K system is directly involved in the pathogenesis of the acute phase of experimental acute inflammation. A specific inhibitor may modulate inflammatory bowel disease.