We evaluated the change in density of total senile plaques, plaque subtypes, and neurofibrillary tangles, from biopsy to autopsy in left frontal cortical sections from four patients with clinically typical Alzheimer's disease (AD). Comparisons were made on sections stained with modified Bielschowsky and Thioflavin S. In two cases, comparisons were also made on tissue stained with a monoclonal Alz-50 antibody and an antiserum to A beta (beta-amyloid protein). Despite a marked decline in mental status over several years of follow-up clinical evaluations, there was no consistent significant change in numerical density of plaques or tangles among the four cases. However, we did find fewer primitive plaques in the autopsy specimens. These results from longitudinally evaluated persons with typical AD suggest that although plaques and tangles may serve as adequate markers of the presence of AD, their numerical density within a single neocortical region may not reflect dementia severity. This conclusion supports the results of recent cross-sectional studies on the progression of pathology among persons with AD.