Background Intracranial hemorrhage is the most feared and lethal complication of oral anticoagulation. We review the frequency, predictors, and prognosis of this most common neurological complication of oral anticoagulation. Summary of Review Anticoagulation to conventional intensities increases the risk of intracranial hemorrhage 7- to 10-fold, to an absolute rate of nearly 1%/y for many stroke-prone patients. Most (70%) anticoagulant-related intracranial hemorrhages are intracerebral hematomas (approximately 60% are fatal); the bulk of the remainder are subdural hematomas. Predictors of anticoagulant-related intracerebral hematoma are advanced patient age, prior ischemic stroke, hypertension, and intensity of anticoagulation. In approximately half of anticoagulated patients with intracerebral hematoma the bleeding evolves slowly over 12 to 24 hours, and emergency reversal of anticoagulation is crucial. Conclusions Both patient factors and anticoagulation intensity importantly influence the rate of anticoagulation-related intracranial hemorrhage. Patient-related risk factors for this complication overlap with those for ischemic stroke. The risk/benefit equation of anticoagulation for elderly, stroke-prone patients is complex and differs from that for younger patients. The absolute rate reduction (not the relative risk reduction) of ischemic stroke by anticoagulation is the critical issue and must offset accentuation of often lethal brain hemorrhage.