This article is part of my series of articles that deal with the Western and Chinese commercial disputes from the 1880s until the outbreak of the Sino-Japanese War. In contrast to my previous articles, it deals with commercial disputes between American mercantile firms and Chinese trading merchants in the early twentieth century by examining the unpublished Shanghai American consular archives at NARA II (National Archives and Records Administration), College Park, Maryland. Together with correspondence in the North-China Herald (NCH), these archives can be materials for revealing the peculiar behavior of the proprietors of Chinese partnership (joint-share, or hegu 合股) firms. They cooperated with American mercantile firms so long as the assets of American mercantile firms could guarantee their commercial profits. Whenever they were aware that American mercantile firms could no longer guarantee the safety of their commercial assets, they did not hesitate in breaching commercial contracts by means of various tactics. Seen from the American side, it was nothing but a betrayal. Following typical cases in the records, this article reveals the process by which these commercial disputes escalated to such a level that leaders of Chinese mercantile people demanded reforms to the commercial court system at the end of the 1910s.