Dr. MacNeill received a Bachelor of Science in Mathematics from Eckerd College. Upon graduation he was named a Joseph Wharton Fellow for graduate study at the Wharton School of Finance, University of Pennsylvania. These studies were interrupted by a four year enlistment in the U.S. Army, serving in both Vietnam and at the National Security Agency near Washington, D.C. He was awarded two Bronze Stars during his tour as a Vietnamese linguist.

After leaving the Army, Dr. MacNeill returned to Atlanta and enrolled in pre-med course work at Georgia Tech, then earned his Doctor of Medicine degree from Emory University School of Medicine. While at Emory he worked for the Center for Disease Control in the departments of Nutrition and Small Pox Eradication. After completing his anesthesia residency at Emory University Hospital he was employed as a staff anesthesiologist by the anesthesia practice affiliated with St. Joseph's Hospital of Atlanta. Dr. MacNeill opened the Pain Center at St. Joseph's Hospital in 1981 and served as its Medical Director until leaving to join The Physicians' Pain & Rehabilitation Specialists of Georgia, P.C. in 1996.

Dr. MacNeill has been Board Certified in Anesthesiology since 1983 and received the Subspecialty Certification in Pain Management in 1993. He is president of the Greater Atlanta Pain Society for the 1999 - 2000 term and is a member of the Greater Atlanta and American Societies of Anesthesia, the International Anesthesia Research Society, the American Society of Regional Anesthesia, the American Pain Society, the Medical Association of Atlanta and the American Medical Association