Senile dementia of the Alzheimer type (SDAT) is typified pathologically by neuritic plaques (NP) and neurofibrillary tangles (NFT) in the neocortex and hippocampus. However, in a large series of cases (60) over age 74 a significant minority (30%) lacked neocortical tangles. In order to determine if these latter cases (Group B) otherwise differ from the majority which have both neocortical plaques and tangles (Group A), various clinical and neuropathological parameters were measured for both groups and the results compared. The following indices were examined: degree of dementia, rate of progression of dementia, age at death, brain weight, cerebral hemispheric weight, cortical cell counts from the frontal, temporal, and parietal lobes, the number of neocortical NP, the number of hippocampal NP and NFT, and the levels of neocortical choline acetyltransferase and somatostatin. The two groups showed no statistically significant differences in any of these categories except for increased numbers of neocortical NP in Group A in midfrontal and superior temporal regions. However, cases in Group A showed greater pathologic abnormality in nearly every parameter, albeit without attaining statistical significance. We conclude that SDAT with neocortical NFT is the same disease as SDAT without them, although the presence of such tangles is associated with a tendency towards greater severity.