Among several hypothesis for the development of Alzheimer's disease is a viral hypothesis. The present study was designed to detect nucleic acid sequences for conventional viruses in peripheral blood cells and brain of Alzheimer's disease patients. DNA was isolated from peripheral blood cells and brain tissue from control individuals and Alzheimer's disease patients. Southern blot analysis was performed using radiolabeled probes for various conventional viruses. The results fail to detect the presence of Herpes simplex 1 (HSV-I), Herpes simplex II (HSV-II), Epstein-Barr virus (EBV) and cytomegalo virus (CMV) at a sensitivity level of detecting 1 genome/100 cells. We exclude conventional viruses as a cause of Alzheimer's disease at this level of detection.