Individual cognitive profiles and correlations between cognitive functions and regional cerebral blood flow (rCBF) were analyzed in 20 consecutive patients with a clinical diagnosis of probable Alzheimer's disease (AD). CBF was measured with high resolution single photon emission computed tomography (SPECT) and [(99m) Tc]d,l-HMPAO. The analysis of cognitive profiles was based on the composite scores for six cognitive domains, derived from a detailed neuropsychological test battery, as compared with corresponding test data obtained in a control group of 28 age-matched healthy volunteers. The cognitive profiles displayed a marked heterogeneity as concerned the general level of cognitive impairment, the number of significantly affected cognitive domains, the spectrum of affected and non-affected cognitive domains, and the severity of each cognitive dysfunction. Statistically significant correlations with rCBF were found for memory scores (right frontal and temporal cortex), abstraction scores (frontal/parietal ratio of rCBF), language scores (left frontal and temporal cortex), visual perception scores (rCBF throughout the right hemisphere), and for visuo-construction scores (side-to-side asymmetry of parietal rCBF). We conclude that the previously observed topographical heterogeneity of rCBF distribution patterns in probable AD was reflected by differences in cognitive profiles. The observed heterogeneities stress the relevance of analyzing individual cognitive and rCBF data, as a supplement to group comparisons of data, in the investigation of diseases with potential heterogeneous affections of the brain.