Simon Flexner (1863-1946), like his brother Abraham Flexner, was a prime mover in U.S. medical education and research. At the same time that Abraham's 1910 book on medical education was stimulating widespread reform in medical schools, Simon was leading a pioneering effort in biomedical research and scientific research directed at medical issues. Simon was instrumental in the founding of the Rockefeller Institute of Medical Research, which later became Rockefeller University, and served as its first director from 1902 to 1935. He also convinced the Rockefeller Foundation in 1919 to support the National Research Council Fellowships, which were the primary source of U.S. medical and scientific postdoctoral support for four decades. One of the early NRC fellows was Detlev Bronk, who later became president of Rockefeller University. Simon Flexnor's enduring influence on higher education and research will be evident as Rockefeller University celebrates its centennial in 2001.