During his last year as the NIH director, Marston became embroiled in a funding controversy with the Nixon administration, which wanted to place greater funding emphasis on a "war on cancer." Marston believed that emphasizing one disease at the expense of other medical research was bad policy, and continued to support balanced, comprehensive funding priorities. He eventually resigned from NIH in April 1973, after nearly five years as director. Afterward, he became a scholar-in-residence at the University of Virginia in Charlottesville, Virginia. The National Academy of Science's Institute of Medicine named him as its inaugural distinguished fellow.