A biochemical mapping of neurofibrillary degeneration was performed in Brodmann areas of the brains of five patients with senile dementia of the Alzheimer type (AD). To quantify the degenerating process, we used an immunoblot method with antibodies directed against the abnormally phosphorylated tau proteins named Tau 55, 64 and 69, known to be early and reliable markers of the degenerating process in AD. The detection intensities were assessed using a numerical rating scale for each area and scores were grouped by lobe. In all cases, the detection of Tau 55, 64 and 69 was positive in all areas except in primary visual cortex (area 17) for two patients. The detections were especially strong in temporal neocortical and limbic areas and were higher in associative cortex than in primary sensory cortex. Scores from the occipital and frontal lobes differed strongly between patients as compared to the uniform degree of detection in the limbic, temporal and parietal lobes. Despite a relatively identical duration of the disease and an apparently global involvement of the cerebral cortex, the distribution of neurofibrillary degeneration in AD varies significantly across cortical areas and displays striking heterogeneity patterns along the rostrocaudal axis. The immunodetection of abnormal tau proteins using the Western blot method may provide complete and rapid quantitative data of the degenerating process in AD.