With more than 4 million Alzheimer's victims nationwide, there is intense research to elucidate the relationship among the hallmarks of the disease, amyloid plaques, neurofibrillary tangles, and degeneration of the basal forebrain cholinergic neurons. There has been much debate about which of these is the primary lesion, and which develops secondarily. The correlation between plaques and tangles and dementia is not absolute, but a consistent feature of Alzheimer's disease is loss of cortical and hippocampal cholinergic function as a result of basal forebrain compromise. Additionally, factors associated with the cholinergic system have been shown to influence the processing and metabolism of the amyloid precursor, a protein that contains the amyloidogenic sequence found in plaques. In this paper, the relationship between cholinergic compromise and amyloid deposition, as well as the cholinergic system-associated factors which appear to participate in amyloid precursor protein processing, are discussed.