Dr. Sidney Alexander, a distinguished cardiologist and co-founder of Physicians for Social Responsibility, passed away at the age of 94 on May 26 at his home in Newton, Massachusetts. He was recognized for his pioneering work in preventive cardiology and his advocacy against nuclear weapons, which culminated in the organization sharing the Nobel Peace Prize in 1985. Dr. Alexander had a profound impact on his patients and colleagues, remaining active in patient care until shortly before his death. His contributions to cardiology included early work in cardiac defibrillation and lipidology, and he was a passionate mentor to many. An avid runner, he authored the book 'Running Healthy,' which encouraged physical activity for heart health. Born in Hartford, Connecticut, he was the first in his family to attend college, graduating from Wesleyan University and Harvard Medical School. He is survived by his wife, two daughters, five grandchildren, and two great-grandchildren. A celebration of his life and work will be announced.