A total of 160 patients with Alzheimer-type dementias (ATD), including 84 with Alzheimer's diseases (AD) and 76 with senile dementia (SD), were examined. The initial signs of the disease were analyzed by making a retrospective assessment of informative history data. The prospective follow-up involved clinical, neuropsychological and electrophysiological (EEC mapping, evoked potentials) studies by applying the standardized assessment of results. There was shown to be a set of clinical and paraclinical parameters for the status of ATD patients, indicating a distinct-quantitative and qualitative difference between patients with AD and those with SD and supporting the heterogeneity of ATD.