In 1907 he was sent to investigate rising anti-Japanese sentiment in San Francisco and Vancouver, B.C. He helped negotiate the “gentlemen's agreement” between Japan and the United States, by which the Japanese government promised to withhold passports from labourers intending to migrate to the United States. In 1917 he negotiated the Lansing–Ishii Agreement, in which the United States rather ambiguously acknowledged Japan's special interests in China, while Japan affirmed its respect for the U.S. Open Door policy, which sought to preserve China's independence and territorial integrity and to allow all nations equal trading rights with China (at that time outside nations were trying to carve China into special spheres of influence). Ishii was killed in a U.S. bombing raid during World War II. His memoirs, Gaikō yoroku, have been partially translated into English as Diplomatic Commentaries.