Duplex and transcranial sonography make non-invasive assessment of cerebrovascular hemodynamics possible. Lesions of the carotid bifurcation are divided into the categories I-VI by which the different forms of carotid lesions are defined. Pathological alterations of the major basal cerebral arteries as well as the quality of collateral circulation via the ophthalmic artery and the circle of Willis are readily picked up and evaluated by transcranial doppler sonography. If cerebrovascular disease is suspected it is therefore recommended to proceed first with duplex and transcranial sonography. If the results are negative, then echocardiography is indicated. With these non-invasive methods a correct diagnosis can usually be made. Patients who are at great risk of suffering a stroke are integrated into a programme aimed at prevention of cerebrovascular insults and re-insults. This programme includes the elimination of the usual risk factors and specifically the medication of anti-platelet drugs or oral anticoagulants respectively in cases of cardiac embolism. In special well-defined cases endarterectomy of the carotid bifurcation might be indicated. Regular clinical examinations will enable a long-term follow-up and permit assessment of the efficacy of a preventive programme while simultaneously increasing patient compliance.