Biomarkers as aids to diagnosis, prognosis, and effective therapies have become holy grails of translational neuroscience. In neurodegenerative disorders, especially Alzheimer disease (AD), imaging and cerebrospinal fluid (CSF) biomarkers for the amyloid-β (Aβ) protein and tau have found their place in research and clinical trials, enabling much more accurate diagnosis. Despite these advances in diagnostic biomarkers, less progress has been made with respect to biomarkers of progression. Alzheimer disease progresses slowly and has a long preclinical stage prior to clinical manifestations; biomarkers of progression could provide invaluable information to assess the efficacy of potential disease-modifying agents in clinical trials. If medicines modify disease progression by slowing neurodegeneration in the brain, the neurodegeneration biomarker should also be modified.1