Ten cases of atherothrombotic brain infarction, 10 cases of cardioembolic brain infarction, 10 cases of lacunar brain infarction, 10 cases of transient ischemic attack (TIA) and 10 age-matched controls were studied. The cerebral blood flows in the cerebral cortex and cerebral white matter were significantly lower in the atherothrombotic, cardioembolic and lacunar infarction groups than in the TIA and control groups. The acetazolamide reactivity in the cerebral cortex was significantly lower in the atherothrombotic and lacunar infarction groups than in the cardioembolic, TIA and control groups. The rate of association of hypertension was significantly higher in the atherothrombotic, lacunar and TIA groups than in the cardioembolic and control groups. Plasma fibrinopeptide A, platelet factor 4 and beta-thromboglobulin concentrations were higher in the atherothrombotic, cardioembolic and lacunar groups than in the TIA and control groups. The present study suggests that the degree of thrombolysis and platelet activation is less in TIA than in cerebral infarction and that underlying cerebral arteriosclerosis is more severe in atherothrombotic and lacunar infarction than in cardioembolic infarction.