Indications for anticoagulant treatment to prevent thromboembolic disease have increased in recent years. INR must be monitored frequently to determine the safest dose and to minimize the risk for thrombotic and haemorrhagic complications. Standard warfarin therapy is associated with rates of major haemorrhage of up to 5-9% annually and recurrent venous thromboembolism of up to 8%. These event rates are dependent of the model of care used to manage warfarin therapy, with better outcomes associated with home testing of the INR which enables patients to monitor their response to warfarin more frequently. INR results must still be 'managed' by communicating the data to the healthcare provider, usually be telephone or fax.