SummaryComputed cranial tomography was performed on 48 patients with Senile Dementia of the Alzheimer Type (SDAT) who have since been followed up in a continuing prospective study. At six-months follow-up, ten patients had died; these did not differ significantly from the survivors either in mean age or duration of dementia, although the latter tended to have been shorter in the deceased. Despite having shorter histories, the deceased had performed worse on initial testing with several cognitive measures, and this was significant for the mental test score; this suggests some patients may have a more rapidly progressive form of SDAT. In a comparison between the CT scan of the deceased and survivors, the deceased were found to have significantly lower mean attenuation densities in the parietal, occipital, and left thalamic regions. The hypothesis that low attenuation density in the parietal regions of the CT scan in SDAT is associated with a more rapid demise is supported for the present period of follow-up.