A variety of different pathogenetic mechanisms are responsible for acute cerebrovascular ischemic events. A certain determination of these mechanisms is essential for specific treatment. In this study the pathogenetic mechanism and clinical course of ischemic strokes in 1770 patients are retrospectively registered for the years 1984-1991. Patients who were admitted to the neurological department of a community hospital during three days were studied. The study group included 298 (16.8%) patients who suffered a TIA, 346 (19.5%) patients with minor stroke and 1126 (63.6%) patients with major stroke. In 41.9% (617/1472) patients with ischemic infarction (minor and major stroke) the pathogenetic mechanisms remains unknown. In patients with ischemic infarction demonstrated on CT scan a pathogenetic mechanism could be defined in more than two-thirds of the cases. 79.5% (1408/1770) of all patients underwent a CT scan. These results underline the importance of a CT scan for the definition of the pathogenetic mechanism. Considering the clinical course in association with the pathogenetic mechanism, patients with small-vessel disease have a good prognosis while patients with in situ thrombosis and cardiogenic embolism have a relatively poor outcome.