In 1956, he received a two-year scholarship for postgraduate training in cardiothoracic surgery at the University of Minnesota, Minneapolis, United States under open-heart surgery pioneer Walt Lillehei.[1] It was during this time that Barnard first became acquainted with fellow future heart transplantation surgeon Norman Shumway, who along with Richard Lower did much of the trailblazing research leading to the first successful human heart transplant.[1] In 1958 he received a Master of Science in Surgery for a thesis titled "The aortic valve – problems in the fabrication and testing of a prosthetic valve".[1] The same year he was awarded Doctor of Philosophy degree for his dissertation titled "The aetiology of congenital intestinal atresia".[1] Barnard described the two years he spent in the United States as "the most fascinating time in my life."