Theme Issue Editorial Focus coagulation (14-16). Similarly, deficiency in the receptors thrombomodulin and endothelial cell protein C receptor, which are required for the generation of activated protein C, causes embryonic lethality (17, 18). Mice expressing low levels of protein C or thrombomodulin with reduced anticoagulant activity have been generated and have proved useful in revealing organspecific functions of the activated protein C anticoagulant pathway. For instance, mice expressing thrombomodulin with reduced anticoagulant activity have different amounts of fibrin deposition in different tissues. These studies support the concept of vascular bed-specific haemostasis described by Rosenberg and Aird (19), which proposes that each vascular bed has a different repertoire of anticoagulants. The role of thrombomodulin in haemostasis and thrombosis in mice is reviewed by H. Weiler (20).