Background: Some investigators studied the relation between carotid artery stenosis and cognitive functions and they found that, patients with carotid artery stenosis performed more poorly than healthy subjects in some cognitive tests. Objectives: The aim of this study is to assess the relationship between asymptomatic carotid stenosis, neuropsychological test performance, and silent brain MRI lesions. Methods: 10 subjects with ultrasound assessed moderate and severe carotid stenosis and 10 healthy control subjects were included in the present study. All subjects were subjected to: complete neurovascular examination, laboratory investigations, carotid and transcranial duplex, MRI brain, ECG, echo cardiography and cognitive assessment using tests for global and specific cognitive functions. Results: In comparison to the control group, subjects with carotid stenosis had significantly lower levels of performance in tests of memory, language, executive functions, verbal memory and visuospatial functions, independent of MRI lesions. White matter hyperintensities were more prevalent than lacunar infarction in the patients group. Also a negative correlation was found between the degree of carotid stenosis and the performance on tests of memory and executive functions, and that subjects who had bilateral carotid artery stenosis had a lower level of performance than subjects with unilateral stenosis in tests of attention, memory and executive functions. Conclusion: Carotid stenosis was associated with poor neuropsychological performance. This could not be explained by a higher proportion of silent MRI lesions in asymptomatic persons, making it less likely that cognitive impairment was caused by silent emboli.