Thirteen women with senile dementia of Alzheimer's type (SDAT) according to NINCDS-ADRDA and 21 age-matched control women, aged 75-96 years, were investigated with clinical examination, dementia rating scales and single photon emission computed tomography (SPECT) using 99mTc-hexamethylpropyleneamine oxime (HM-PAO) as a tracer of regional cortical blood flow. The aim was to study whether typical SPECT findings of SDAT were seen also in the very old having the disease for a longer period. Neuropsychological assessment with vocabulary and spatial tests was performed in the control women, and the results were divided in three subgroups, normal, borderline and abnormal. Regional perfusion values, expressed as a ratio between cortical and cerebellar HM-PAO uptake, were lower in frontal, temporoparietal and occipital cortices in SDAT patients than in controls. The SDAT patients had the lowest uptake in the posterior temporoparietal region (0.67 +/- 0.06) and the corresponding value in the controls (0.79 +/- 0.05) differed significantly, p < 0.0001. The interhemispheric ratio between right and left posterior temporoparietal regions was 0.99 +/- 0.05. Nine of the control women (43%) had pathological SPECT with hemispheric asymmetries in 6 cases and bilateral temporooccipital reductions in 3 women. The neuropsychological assessment matched the findings in 7 of these women. One of the control women was judged as pathological and 10 women as borderline according to the spatial and vocabulary tests. Four of the 10 women with borderline results had normal SPECT. The sensitivity of the assessment to detect abnormalities compared to SPECT was 78% if borderline and abnormal results were expressed as true-positive cases. The specificity was 67%.(ABSTRACT TRUNCATED AT 250 WORDS)