Stroke prevention is extremely cost-effective. The Ontario Task Force for the Coordinated Stroke Strategy for Ontario received from Dr. Muhammad Mamdani of the Institute for Clinical Evaluative Sciences the estimate that stroke prevention is approximately ten times more cost-effective than treating acute stroke with tPA.1 Hackam and Spence2 have calculated that in the highest-risk patients it would be possible to reduce the risk of stroke by more than 90% by a combination of interventions (including blood pressure control, smoking cessation, diet, treatment of diabetes, lipid-lowering therapy, and for patients in whom it is indicated, anticoagulation for atrial fibrillation or carotid endarterectomy). Dr Mukul Sharma (personal communication) has shown that stroke prevention is a dominant strategy in health economic terms; i.e. that it improves outcomes while reducing net costs. Effective control of hypertension has the potential to reduce stroke by half.3,4 Because hypertension is so prevalent, it accounts for the greatest population attributable risk for stroke, and thus represents the greatest opportunity to reduce stroke.