In patients >75 years of age, the two main indications for oral anticoagulant therapy with vitamin K antagonists (VKAs) are treatment of venous thromboembolic disease and prevention of systemic embolism in patients with nonvalvular atrial fibrillation. In both indications, a target International Normalized Ratio of 2.5 (range 2.0-3.0) is recommended. Bleeding is the adverse effect feared by physicians that most limits the use of VKAs in older frail patients. In this paper, we discuss (i) the risk of VKA-related bleeding with advancing age; (ii) the severity of bleeding complications and particularly the risk of intracranial haemorrhage in older patients; (iii) the risk factors for bleeding related to patient characteristics; and (iv) the risk factors or determinants for bleeding related to treatment variables (warfarin induction and maintenance administration, instability of anticoagulation, poor compliance and patient's education level, and concomitant use of drugs). Avoiding over-anticoagulation and/or reducing periods of overdosing in the course of oral anticoagulant treatment with tailored monitoring may help to minimise the risk of bleeding in older patients.