In 1961, MacLeod became the chairman of the Life Sciences Panel of President John F. Kennedy's Science Advisory Committee. In 1963, Kennedy appointed MacLeod as Deputy Director of the Office of Science and Technology, Executive Office of the President (now the White House Office of Science and Technology Policy). MacLeod was the first person to hold the position of deputy director of OST and remained there until 1966, serving as an advisor to President Lyndon B. Johnson after Kennedy's assassination. It has not been possible to find documents that confirm who conceived of a collaborative medical research enterprise between the United States and Japan. However, the idea is often attributed to MacLeod, who became chairman of the first U.S. delegation to the USJCMSP in 1965.