A. SPECIFIC AIMS Long-term oral anticoagulant therapy with warfarin is essential for the prevention of strokes and other thromboembolic events related to various medical conditions that increase in prevalence in older persons. However, the desire to initiate anticoagulant therapy in an older patient is tempered by concerns about the risk of bleeding. The residents of nursing homes are among the most frail patients in the geriatric population and are at increased risk for drug-related iatrogenic injury not only because of the physiologic declines and pharmacologic changes that occur with aging, but also because of the special clinical and social circumstances that characterize this setting of care for more than 1.7 million Americans who reside in an estimated 16,000 nursing homes across the United States.