The neuropsychological deficits in 5 patients with chronic and MRI-proven unilateral infarctions in the perfusion teritory of the paramedian thalamic arteries were studied. All patients showed deficits pointing to a dysfunction of frontotemporal hemispheric structures on the side of the thalamic lesion. However, 4 patients revealed additionally neuropsychological deficits pointing to a dysfunction of frontotemporal hemispheric structures overlying the nonaffected thalamus. The contralateral deficits showed (in 4 patients) signs of temporal and (in 3 patients) frontal lobe dysfunction. It is suggested that the bilaterality of the neuropsychological deficits results from additional contralateral thalamic lesions not detected by MRI and/or from bilateral cortical hypometabolism.