Cardiovascular anomalies contributing to development of atrial fibrillation (AF) and subsequent cerebral repercussion have been studied by analysis of clinical, electrocardiographic and anatomicopathological data for 131 elderly (85.16 +/- 6.7 years) medium- and long-term hospital patients. AF was seen in 22.14% of cases and seems more frequent in the ninth decade than in the eight. Predisposing factors were coronary alterations of repolarization (p less than 0.001), myocardial hypertrophy (less than 0.01), hypertension with cardiac repercussions (p less than 0.01), intraventricular conduction disorders, left anterior hemiblock excepted (p less than 0.05) and mitral valvulopathy. AF developed in 12% of cases without apparent cardiopathy. The risk of cerebral infarct was marginally greater in the presence of AF than in its absence; the risk was clear for paroxysmal forms and nil when AF developed in a healthy heart. In contrast, intellectual deterioration and cerebral hypotrophy were significantly more marked (p less than 0.01) in patients presenting AF. This affirmation is evidence for long-term hemodynamic repercussions of arrhythmia affecting cerebral blood flow and constitutes an argument for re-establishment of sinusal rhythm.