Cultured confluent human umbilical vein endothelial cells were incubated with new-breviscapine (NB), a flavonoid consisting of 4-OH-scutellarin-7-O-glucuronide (C33H30O18) and FeCl3, MgCl2, and CaCl2, which is first extracted from Erigeron breviscapus (Vant) Hand-Mazz in China, 0, 6.25, 12.5, 25, 50, 100, and 1,000 micrograms.ml-1. The releases of tissue-type plasminogen activator (t-PA), and epoprostenol (Epo) from endothelial cells were stimulated by NB, but no significant effect of plasminogen activator inhibitor (PAI) activity was seen. NB 25-1,000 micrograms.ml-1 induced a production of thrombomodulin (TM) within the cells, an expression of TM on the surface of the cells, and a release of TM from the cells. Our data provide a new evidence that NB is a stimulant to fibrinolysis and anticoagulation of endothelial cells.