The conversion of plasminogen to plasmin is a key event in many physiological and pathologal processes requiring regulated extracellular proteolysis. Direct focal degradation of proteins involved in cell-cell and cell-matrix interactions by plasmin has been described, js as well as activation of other degradative enzymes, notably the matrix rnetall~ proteinases~(MMPs). Complex control of the plasminogen activator cas-cade has been shown to be required for the movement and re-organization of cells and matrix in events such as ovulation, trophoblast implantation, embryogenesis, and angiogenesis, as well as in the invasion and metastasis of tumors. A further level of regulation is thought to be effected by the release by plasmin of matrix-sequestered growth factors, such as basic fibroblast growth factor and trdnsbrming growth factor