The extent of infarct area (IA) on CT-scan in 104 patients with ischemic stroke (IS) was compared with the presence of atrial fibrillation (AF) and other risk factors (hypertension, dyslipidemia, alcohol abuse). Infarct size was also compared with biological and clinical parameters in acute stage (6-12 h) (blood glucose level, systolic and diastolic arterial pressure, haematocrit, consciousness, clinical picture) and with clinical outcome. Among risk factors, only AF showed a significant correlation with IA extension (p less than .0009). IA correlated also with consciousness (p = .0017), clinical picture (p = .0145) and with clinical outcome (p less than 10(-6). Patients with AF showed a more severe clinical outcome with respect to patients without risk factors. It could be hypothesized that patients with AF have a reduced capacity for increasing or sustaining cerebral blood flow in the acute phase of IS.