The brain is the most compartmentalized organ. It is also highly aerobic. Because nerve cells grow but do not regenerate, the brain is the organ best suited for the accumulation of metabolic errors colocalized in specific areas of the brain over an extended period. Alzheimer's disease (AD) is primarily a neurological disorder of the elderly. It is suggested that this disorder results from the accumulation of such errors, and that AD onset aluminum and iron contribute to but do not necessarily initiate the onset of the disease. In vitro and in vivo evidence summarized here suggests that this is effected by interfering in the utilization of glucose and glucose-6-phosphate, and sequestration of iron by ferritin. beta-amyloid precusor proteins (beta-APPs) are normal components of the human brain and some other tissues. Proteolysis of these, presumably by serine proteases, generates a 39 to 42 amino acid long peptide, the alpha-amyloid (beta-AP). In AD brains, beta-AP aggregates into plaque, the hallmark of AD brains. Some of the alpha-APPs also contain a 56 amino acid long segment which inhibits serine proteases. We show that in vitro, at pH 6.5, aluminum activates beta-chymotrypsin 2-fold and makes it dramatically resistant to protease inhibitors such as bovine pancreatic trypsin inhibitor (bPTI) or its mimic present in the beta-amyloid precursor proteins (beta-APPs). Iron and oxygen are reported to favor cross-linking of beta-AP in vitro.(ABSTRACT TRUNCATED AT 250 WORDS)