Identification of risk factors and biomarkers of neurodegenerative disease is essential in caring for the growing numbers of elderly. Imaging biomarkers provide non-invasive ways to look at brain function. A new PET imaging agent, Pittsburgh Compound B (PiB), that identifies brain amyloid is an exciting development in brain imaging that needs to be studied. We plan to study this imaging technique in normal volunteers and patients with a variety of neurodegenerative diseases to determine its utility. Long term followup of these subjects will allow us to understand the predictive ability of this new test.