INTERVENTION All patients considered for the study will be introduced to the idea of PSM and theory behind anticoagulation in a normal office visit with a physician of approximately half an hour. The consent form will also be explained and given to the patients. They will then return for a follow-up in approximately one week after considering the undertaking. If participation is desired and consent is obtained the patient will be randomized into either group A or group B. Patients of group A will have the task of managing their own warfarin therapy using the provided nomograms. Patients of group B will continue to be managed by their physician. In the second office visit patients will be told to which group they were randomized and if they are in group A they will then be instructed on how to use the warfarin adjustment nomograms provided. After four months the groups will switch to the alternate management strategy. This time those in group B will be instructed on how to use the nomograms during an office visit. Patients in both groups will use warfarin tablets of two dosage strengths, 1 mg and 5 mg. All INR testing will be done at the community laboratory and results will be made available to the patient for dosage adjustment, as well as the physician. The physician's office will be available for appointments and phone calls from study subjects to discuss and support the process at any time.