Alzheimer's disease (AD) affects millions of people throughout the world. The financial and emotional costs that are inflicted by this devastating disease are enormous. Genes responsible for the early-onset familial AD have been cloned and found to be membrane associated transport proteins. Evidence suggests that apolipoprotein E4 may be the risk factor for the late-onset form of the disease. Beta-amyloid and potassium channel dysfunction have also been implicated in the development of AD. Hyperphosphorylation of "tau" has been indicated for the generation of neurofibrillary tangles in the brains of Alzheimer's patients. Since apoE4 does not bind to "tau", apoE4 may contribute to the hyperphosphorylation of "tau" which may cause the formation of neurofibrillary tangles in AD patients. Molecular biology research on AD should help in the development of drugs for the prevention and treatment of the disease.