The ME Association profile describes Dr. William Weir as a retired physician who has treated ME/CFS patients for many years and who still sees them privately. During his tenure as a consultant in Infectious and Tropical Disease at the Royal Free Hospital in London, he began seeing patients whose acute infections had been effectively treated but who remained unwell with what is now recognized as ME/CFS. He has been advising the National Institute for Health and Care Excellence (NICE) on the new clinical guideline for ME/CFS and co-authored an article with Dr. Nigel Speight titled 'ME/CFS: Past, Present and Future' published in August 2021. Dr. Weir advocates for scientific research over psychological theorization and has been a vocal critic of Graded Exercise Therapy (GET) as harmful for ME/CFS patients.