The inhibitory actions of Ulinastatin, which is a protease inhibitor, on the production of polymorphonuclear leukocyte elastase (PMN-elastase) and interleukin 8 (IL-8) in vascular endothelial cells were evaluated. Our findings suggest that IL-8 plays a role in the production of PMN-elastase. Ulinastatin inhibited the lipopolysaccharide (LPS)-stimulated activity of polymorphonuclear leukocytes (PMN) and the production of IL-8 in vascular endothelial cells. Ulinastatin also inhibited the LPS-stimulated production of PMN-elastase in PMN.