Post-mortem Alzheimer’s diseased brain specimens reveals significant levels of Aß (11-40/42) within insoluble amyloid pools. The ß-secretase enzyme or ß-amyloid precursor protein-cleaving enzyme (BACE) generates the N terminus of Aß, ultimately leading to the production of full-length Aß (1-40/42) or truncated Aß (11-40/42). The abundance of Aß (11-40/42) produced by BACE suggests that their roles in AD pathogenesis may be important.