Dr. McMillan is Editor-in-Chief of the textbook Oskis Pediatrics: Principles and Practice and Editor-in-Chief of Contemporary Pediatrics. She served as medical editor of the Infectious Diseases Sub-Board Examination for the American Board of Pediatrics for 15 years and was a member of the American Academy of Pediatrics Committee on Infectious Diseases from 2001-2007. She currently serves on the Pediatrics Review Committee for the Accreditation Council for Graduate Medical Education.

Dr. McMillan has served as Chair of the Board of Directors of the American Board of Pediatrics and on numerous committees of the Board. She is a representative of the ABP to the American Board of Medical Specialties, and she is a member of the Infectious Disease Society of America, the Pediatric Infectious Disease Society, and the American Academy of Pediatrics.