The optimal duration of anticoagulant therapy for the treatment of venous thromboembolism has been the subject of many randomised trials over the past 15 years.1 2 The results indicate no clear advantage for many patients of prolonging warfarin beyond three to six months, because of the risk of bleeding and the inconvenience. The annual incidence of major bleeding in patients who take warfarin for longer than three months is 2-3%, with an estimated case fatality rate of 9.1% (95% confidence interval 2.5% to 21.7%).3 Also, duration of treatment has little effect on the long term risk (after the first three months) of recurrence. Trials have shown that the frequency of recurrence at two to three years is similar in patients taking three months or 12 months of oral anticoagulation.1 2 …