We studied the cognitive significance of ventricular enlargement in 40 vascular patients with leuko-araiosis on MRI. We obtained significant differences between patients and normal controls without vascular risk-factors regarding ventricular measures. Ventricular size of the patients correlated with several neuropsychological tests measuring abstract reasoning, comprehension of language, constructional skills, speed and attention. These results suggest that ventricular enlargement in vascular patients reflects global deterioration of complex cognitive functions. Information proceeding from ventricular size is complementary to that coming from the degree of leuko-araiosis and probably has more clinical significance. Both leuko-araiosis and ventricular size may be neuroimaging parameters capable of reflecting the cognitive deterioration in vascular patients without large lesions.