Seven cases of Alzheimer's disease were studied in detail from a clinical and neuropathological point of view. The degenerative process was mapped with regard to regional variations in the intensity, extent and consistency of focal accentuations. The degeneration was regularly found to be most pronounced in certain areas: maximal cortical degeneration occurred in the medial temporal (limbic) area and, in the lateral hemisphere, consistently within a field expanding from the posterior inferior temporal areas to the adjoining portions of the parieto occipital lobes. In addition, the posterior cingulate gyrus was severely involved. On the other hand certain areas were notably and consistently spared or less involved, mainly the anterior cingulate gyrus and the calcarine and central sensory motor areas (primary projection areas). The frontal lobes occupied an intermediate position, being less severely involved than is usually reported. The clinical symptoms correlated well with this pattern of degeneration. Thus groups of symptoms such as memory dysfunction, emotional and personality alterations, and some symptoms of the Klüver-Bucy syndrome, were referable to the limbic lesions. The cortical lesions of the temporo-parieto-occipital association cortex correlated with the symptoms of agnosia, aphasia and apraxia, which were recorded in all cases. The relative sparing of the primary projection areas correspond well to findings of retained motility and perception even in later stages of the disease. The relative sparing of the frontal lobes and the anterior cingulate gyrus was related to the preservation of habitual personality traits. The pattern described may be related to ontogenetic features, and the tendency to focalization to the age of disease onset. The role of genetic factors and of other diseases is discussed.