Dr. Christopher M. Clark, a neurologist and associate professor of neurology in the Perelman School of Medicine, whose research contributed to the clinical and scientific advances that moved Alzheimer’s disease from a poorly understood and rarely diagnosed disease to a widely recognized and common cause of late-life dementia, died of sarcoma on January 12. He was 65 years of age. Dr. Clark’s career was devoted to establishing the US clinical research and clinical trial network for advancing diagnostics and therapeutics in Alzheimer’s disease. He was director of the Duke University Memory Disorders Clinic, and the clinical director of the University’s Joseph and Kathleen Bryan Alzheimer’s Research Center from 1986-1989. From 1990 to 2007, he served as the director of the Clinical Core of the National Institute of Aging funded Alzheimer’s Disease Center at the University of Pennsylvania, as well as the associate director of this Center and was among the leaders in establishing the Penn Memory Center, where he served as director. After retiring from Penn in 2007, Dr. Clark worked as the medical director for AVID Radiopharmaceuticals. He led the investigator team that demonstrated the ability of a brain imaging method (known as an Aβ amyloid PET scan) to detect brain deposits of Aβ amyloid, a type of brain pathology that is widely recognized to be one of the two defining pathologies of Alzheimer’s disease. This research, published in the Journal of the American Medical Association in 2011, is regarded as a landmark study for advancing clinically applicable Alzheimer’s disease diagnostics. The PET scan ligand Dr. Clark evaluated in this study, is currently before the FDA for review and approval. Dr. Clark was one of the founding participants in the Alzheimer’s Disease Cooperative Study, a National Institute of Aging funded clinical trials network that established a national infrastructure for Alzheimer’s disease clinical trials and conducted the first clinical trials in patients with Alzheimer’s disease. He had a particular commitment to developing efficient methods for the early and reliable diagnosis of Alzheimer’s disease that could be readily adopted into routine primary care clinical practice, the evaluation of Alzheimer’s disease treatments, and the relationship between Parkinson’s disease and Alzheimer’s disease. He co-developed the Dementia Severity Rating Scale, a self-administered scale that a family member could complete and whose scores assisted in diagnosing dementia and mild cognitive impairment. He was a mentor to many faculty and staff. Dr. John Trojanowski, director of Penn’s Alzheimers Disease Center and a collaborator with Dr. Clark for nearly 20 years recalls how “Chris was an inspiration to all of us and a beacon of hope to patients with Alzheimer’s and their families. I and my colleagues at Penn, our patients and their families and many in the global Alzheimer community who knew Chris will miss him dearly, but we all are inspired by Chris to continue the effort to create a world without Alzheimer’s disease.” Born in Norfolk, Virginia, Dr. Clark earned his BS degree from Penn State University in 1967 and his MD from Thomas Jefferson University in 1973. He then trained in neurology at Pennsylvania Hospital and Columbia-Presbyterian Medical Center. Dr. Clark is survived by his wife, Anne; stepsons, David Emrich and Matthew Emrich; and his siblings, Anne McLaughlin and Gerry Clark.