In this review I present the hypothesis that a toxic substance, inorganic copper, ingested from drinking water and vitamin/mineral supplements containing inorganic copper, is at least partially causal of the epidemic of Alzheimer's disease (AD) we are seeing in developed countries. I set the stage for this hypothesis by pointing out that the epidemic is a new disease phenomenon coinciding temporally with the use of copper plumbing in developed countries. The evidence is good that AD was nonexistent or rare in the 1800 s and early 1900 s, and the arguments that elderly people did not exist in those times, or that AD was simply attributed to senility, are refuted. The web of evidence tying ingestion of inorganic copper as a causal factor in AD is strong, and includes AD animal model data where trace amounts of inorganic copper in the drinking water markedly worsened AD, human studies where ingestion of copper supplements, along with a high fat diet, is associated with a marked loss of cognition, human studies showing a markedly higher mortality in elderly women ingesting copper supplements, as well as other data. It is likely that a high fat diet works in conjunction with ingestion of inorganic copper to increase the risk of AD. It is clear that some factor toxic to the brain is present in the environment in developed countries, but not undeveloped countries, and is a major risk factor for AD. I believe that that toxic factor is ingestion of inorganic copper.