There is uncertainty about the safety of anticoagulation with warfarin in the elderly. This cohort study investigated the risk factors for warfarin-related bleeding in a primary care setting. In multiple regression analyses increased risk of bleeding was associated with domiciliary monitoring of international normalised ratio (INR), low proportion of INR tests in the target range, high intensity of anticoagulation, and male sex. Age was not associated with increased risk after adjustment. High levels of dependency, not old age, should raise concerns about the safety of anticoagulation with warfarin.