Management of patients with neoplastic disease has shifted from searchand- destroy approaches employing radical surgery, chemotherapy, and radiotherapy to novel strategies that target specific molecular or genetic characteristics or modify growth factors, angiogenesis, and cell-cell interactions. Attention has also been focused on modifying the production and function of certain enzymes pivotal to the genesis of disseminated disease. Serine proteases, the largest human protease gene family, mediate a variety of events relevant to fundamental processes of tumor invasion and metastasis. Other protease types (eg, matrix metalloproteinases [MMPs]) have also been implicated in tumor-cell dissemination. The serine proteases are central to many physiologic processes because they initiate the activation and release of hemostatic, fibrinolytic, and inflammatory mediators. Traditionally, modulation of serine proteases has focused on reducing blood loss and inflammation in the setting of cardiovascular surgery. More recently, serine protease modulation has attracted increasing interest because of the emerging evidence of the roles of these enzymes in cancer. The link between serine protease functions and cancer outcomes suggests that serine proteases might be a suitable target for therapeutic agents aimed at prevention of tumor progression and metastasis. Aprotinin(Drug information on aprotinin) is a broad-specificity serine protease inhibitor first isolated from bovine lung tissue in the 1930s. It acts on the interrelated inflammatory, coagulation, and fibrinolytic pathways to attenuate the systemic inflammatory response, inhibit hyperfibrinolysis, and promote hemostasis.[3-8] Pharmacologic intervention with large doses of a serine protease inhibitor such as aprotinin (Trasylol) is possible in humans, and it may benefit patients by reducing the transfusion burden; by inhibiting certain processes fundamental to an inflammatory response; and by inhibiting enzymes in the coagulation and fibrinolytic pathways that may be involved in the progression from local to disseminated disease. Each of these areas will be discussed in turn in this special supplement to ONCOLOGY, which was developed from discussions held during a closed expert roundtable meeting in Pasadena, California, in February 2003.