The aim of this thesis is to study the opium problem in Guangdong Province between 1858 and 1917. The period of 1858-1917 is a very special stage of opium trade in China, because from 1858 the opium trade became legal in China, and after 1917 all the records of opium import disappeared in the reports of the Chinese maritime customs. During this special period there were large amounts of foreign and Chinese native opium legally or illegally coming into Guangdong, which had a profound influence on the society in Guangdong at the time. This thesis will focus on the opium problem in Guangdong during this special period, including the opium import and significance of opium taxation to maritime customs, and several conflicts relating to the opium problem between different interest groups: foreign customs and native customs, the Chinese central government and local government, Chinese opium and foreign opium, and opium smugglers and preventive officers. It is my contention that the study of these conflicts of interest over opium is a key to understanding the social, economic, and political history of modern China.