ALZ50-based enzyme immunoassay was used to study distribution of Alzheimer's disease-associated protein (ADAP) in postmortem brain tissues of 5 Alzheimer's disease (AD) and 5 non-Alzheimer's disease (NAD) subjects. There are at least three AD-associated proteins, including A68. Levels are higher in brain regions with severe neuronal loss in AD: frontal, temporal, hippocampal cortex, and amygdala. No significant ADAP was found in the NAD samples (from 2 age-matched-1 clinically demented-and 3 younger subjects). ADAP levels in four regions of AD brains were not correlated to neuritic plaque count in corresponding regions of matching formaldehyde-fixed hemispheres.