This study is investigating a possible treatment for Alzheimer's disease with donated cord blood. The trial is being conducted at the Academy of Military Medical Sciences Hospital and the Peking University. The study is currently open but not recruiting subjects. Patients suffering from Alzheimer's disease will receive to infusions of mesenchymal stem cells obtained from donated umbilical cord blood. Participants will be assessed ten weeks after transfusion for any complications and any changes in their cognitive function using standard tests. There is no control group in this study. The trial commenced in March 2012 and is expected enrol 30 patients by February 2014.