A great upsurge in large-scale piracy between 1780 and 1810 had a tremendous impact on the Canton trade. Provincial officials, Hong merchants, and foreign traders repeatedly acknowledged that pirates, operating from bases scattered throughout the Pearl River Delta, greatly hindered commerce and communications. Several times pirates threatened Canton, each time triggering a great panic in the city. To help defray the high costs of defending the city and surrounding delta, officials called on the Hong merchants to “contribute” money. In fact, whenever the government’s coffers were insufficient, the government levied Hong merchants. Periodic exactions were a fact of life for Canton’s Hong merchants, who were assessed monetary quotas for famine and flood relief, construction and repairs of forts and bridges, and for extraordinary military campaign, such as those against the Guangdong pirates. By the 1780s, contributions to the government were usually paid out in installments from the Hong merchants’ common chest, known as the Consoo Fund. This article, which is divided into three sections, examines first, the development of large-scale piracy in the Pearl River Delta in the context of increasingly strained Sino-Western relations; second, the development of a customary contribution system that Qing officials imposed on the Hong merchants and its repercussions on them and the Canton trade; and third, the important role of Hong merchants in the defence of Canton between 1804 and 1810, at the height of the pirate crisis.