Hemophilia and Von Willebrand Disease: Factor VIII and Von Willebrand Factor serves as a must-have reference on the important role these essential blood-clotting proteins play in research and clinical medicine. Clinicians and researchers face the daily challenge of staying current on the vast amounts of research that is now generated. The reference to Janus in the title refers to the two roles of the Factor VIII/Von Willebrand Factor Complex: initiation of coagulation and propagation of clot formation. The complex prevents bleeding in hemophilia and Von Willebrand disease but also augments arterial and venous thrombosis.