Dementia of the Alzheimer type, senile onset (SDAT), and multi-infarct dementia (MID) exhibit differences in cerebrovascular blood flow velocity profiles, which were investigated by means of transcranial Doppler sonography. The pulsatility indices (PI), as angle-independent parameters of peripheral vascular resistance measured in the basal cerebral arteries, were significantly increased in MID patients with respect to SDAT cases. In an analysis of the correlations between several variables and the magnitude of PI, we found strong inverse correlations of the CAMCOG score, and strong direct correlations of the blood pressure and the duration of illness, with the PI of all basal cerebral arteries only in MID patients. In SDAT patients, we found a direct correlation between the Hachinski ischemia score and the PI of all basal cerebral arteries. All 3 ischemia scores (Hachinski, Rosen, Loeb and Gandolfo) were significantly correlated with the PI of the middle cerebral and basilar arteries. By analyzing the correlations of the single items of the 3 different ischemia scores with the PI values obtained, we only found a clearcut correlation with the item focal neurological signs. Thus, our findings stress the relative importance of a concomitant cerebrovascular factor in the development of dementia in old age, even in patients with probable SDAT. A raise of the PI in the basal cerebral arteries allows early suspicion of a cerebrovascular factor even in only slight dementia so that possible risk factors for further aggravation of this type of vascular dementia might be detected and treated early in the course of disease.