A considerable amount of literature has accrued examining the role of copper in the pathogenesis of Alzheimer's disease. Remarkably, there is in vitro and animal data to support both copper toxicity and copper deficiency as relevant mechanisms in Alzheimer's disease. These data have prompted preliminary clinical trials of both copper complexing therapy and copper supplementation therapy, which have yielded mixed results. The preclinical and clinical studies are discussed here in an effort to determine how to move forward with rational clinical trials focused on copper modulation.