In 1980, Barbara Thomas was appointed by President Carter as a member of the U.S. Securities and Exchange Commission (SEC) in Washington, D.C., for a five-year term. Her appointment was widely reported, being the youngest-ever SEC commissioner and only the second woman in the role. She was instrumental in opening U.S. capital markets to foreign companies. She also negotiated on behalf of the U.S. government to open the Tokyo Stock Exchange to foreign members, against opposition from some US financial commentators, who believed that American investors would be uninterested in Japanese stocks. She later described these achievements as among the most significant of her career.