In spite of its wide availability, single photon emission computerized tomography (SPECT) scanning is uncommonly used in the assessment of Alzheimer's disease (AD) and related dementias. In light of recent advances in scanning protocols and image analysis, SPECT needs to be re-examined as a tool in the diagnosis of dementia. A total of 18 subjects with early AD and 10 healthy elderly control subjects were examined with high resolution SPECT during the performance of a simple word discrimination task. SPECT images were coregistered with individual magnetic resonance imaging scans, allowing delineation of predetermined neuroanatomical Regions of Interest (ROI). There was a gradation of regional cerebral blood flow (rCBF) values in both groups, with the lowest values being in the hippocampus and the highest in the striatum, thalamus and cerebellum. Compared to healthy controls, AD subjects demonstrated lower relative rCBF in parietal and prefrontal cortices. Analysis of individual ROI demonstrated bilateral reduction of rCBF in prefrontal poles, posterior temporal and anterior parietal cortex, and unilateral reduction of rCBF in left dorsolateral prefrontal cortex, right posterior parietal cortex and the left cingulate body. There were no significant differences for hippocampal, occipital or basal ganglia rCBF. Discriminant function analysis indicated that rCBF in the prefrontal polar regions achieved the best classification of cases. SPECT has utility in the diagnostic assessment of AD if standardized and semiquantitative techniques are used.