Board-certified internal medicine specialist Ross Pirkle, MD, MS, serves as a physician and advocate for patients at Cornerstone Primary Care in Walnut Creek, California. With degrees from the University of California, Berkeley and the University of California, San Francisco, Dr. Pirkle has practiced medicine in the Walnut Creek area and John Muir Hospital for 2 decades. He served as chief of medicine at John Muir Medical Center for two terms, where he remains a leader in the medical community. Joining Cornerstone Primary Care as a new associate is Robert A. Hardy, MD who is board certified in Internal Medicine and is a Clinical Professor at the University of California, San Francisco School of Medicine. Dr. Hardy is well known and widely respected in the professional community, having held leadership roles in organized medicine at the local, state and national levels.