Plasminogen is the inactive precursor of the blood proteinase plasmin, the enzyme responsible for the dissolution of fibrin clots. It has been recognized for several years, however, that plasmin has a broad substrate specificity and can cleave a number of other proteins, including several components of the extracellular matrix. Specific cell surface receptors for the two major plasminogen activators exist on a number of cell types and probably play an important role in controlling plasminogen activation. The identification of plasminogen fragments that lack enzymic activity but affect cell growth and migration, and the discovery of the plasminogenrelated growth factors, has highlighted previously unsuspected links between blood coagulation and fibrinolysis on the one hand, and regulation of cell behaviour on the other. This book brings together these two lines of work and discusses two main areas: first, the evolutionary and structural relationship between plasminogen-related growth factors and second, the role of plasminogen activation in cell regulation. Chapters in the book deal specifically with the evolutionary and structural links between the clotting and fibrinolytic proteins and the plasminogenrelated growth factors; the role of individual domains for enzymic or receptor binding activity; general features of the receptors for plasminogen-related growth factors and signalling via these receptors; the role of plasmin and the plasminogen-activators in cell regulation and organogenesis; the role of plasminogen-related growth factors in development, in the regeneration of epithelial organs and in angiogenesis; and the role of these growth factors in cancer and in atherogenesis.