Venous thromboembolism (VTE), mainly deep vein thrombosis and pulmonary embolism, is a significant cause of morbidity and mortality in the Western world. It has been estimated that there are 300,000 new cases of first lifetime VTE in the US each year, and there are 60,000 deaths annually from VTE in the UK. Parallels have been drawn with other clinical conditions that have received more attention, and it has been estimated that the mortality rate for VTE in the UK is five times greater than the combined total number of deaths from breast cancer, AIDS and road traffic accidents and more than ten times greater than from methicillin-resistant Staphylococcus aureus infection