The five major risk factors for stroke are hypertension, smoking, diabetes, atrial fibrillation and physical inactivity. All of these are amenable. In addition, although hypercholesterolemia is not strongly associated with stroke in epidemiological studies, primary prevention with statins provides a modest reduction of stroke risk. Unchanged population levels of blood pressure in Sweden over the last two decades are accompanied by constant stroke incidence rates. The single most cost-effective preventive action is detection and treatment of hypertension in the elderly. Antismoking advice and anticoagulants in patients with atrial fibrillation and other cardiac sources of embolism also have favourable effects relative to costs. There is a dearth of successful population-based programs to prevent stroke.