Transient ischemic attacks (TIAs) are reversible neurological deficits due to cerebral ischemia in a vascular territory lasting less than 24 hours, usually less than one hour. The natural course of TIAs is variable. One third of the patients suffer from a subsequent completed stroke with lasting disability, one third of the patients continues to experience TIAs and in one third no further symptoms are encountered. TIAs are a warning symptom of a generalized vascular process, myocardial infarction being the most common cause of mortality and ischemic brain infarction being the most common cause of morbidity. Clinical parameters--besides age--seem to be of minor prognostic relevance. Vascular risk factors should be evaluated in all TIA patients; especially, a cardiac work up including 2D-echocardiography and an exercise stress test should be performed. Duplex sonography of craniocervical vessels shows atherosclerotic lesions in a considerable proportion of patients with TIA; however, localization of these lesions does not always correspond to clinical symptomatology. Some angiographic features are of prognostic relevance. Computed tomography (CT) and magnetic resonance imaging (MRI) show ischemic lesions in a considerable proportion of patients, which connects TIAs directly to ischemic brain infarcts. The extent and localization of these lesions are of some prognostic relevance. Blow flow studies on single photon emission computed tomography (SPECT) and studies of brain metabolism on positron emission tomography (PET) are abnormal in many TIA patients for prolonged periods and also have some prognostic impact. TIA patients probably are a heterogeneous group with a common symptom. A detailed diagnostic work-up may have implications on a more specific and efficient therapy.