As treatment of neurodegenerative disease moves toward therapies aimed at specific molecular abnormalities, the importance of early and accurate diagnosis will increase, as will the need for sensitive measures for tracking disease progression. Brain imaging, using MRI and PET scanning, offers a variety of highly reliable techniques that examine the structure, chemical content, metabolic state, and functional capacity of the brain. For all the major neurodegenerative disorders, relatively specific findings can be identified with some or all of these techniques. New approaches for imaging specific molecular pathology likely will revolutionize brain imaging and be combined with established imaging approaches to obtain a complete molecular, structural, and metabolic characterization, which could be used to improve diagnosis, and to stage each patient and follow disease progression and response to treatment.