This monograph furnishes a social history of narcotics in Manchuria under Japanese occupation (1905-1945). Imperial Japan depended financially on the revenues of the opium traffic in East Asia. I explore the implications of this de jure illegal, de facto legitimate market from the perspective of society. Using the port city of Dairen as a case study, I probe the consequences of the opiate market from the perspective of four overlapping collective participants: discussants, drug users, dealers, and doctors. These communities cut new cleavages of power and payoff across traditional divides of race, nationality, class, and gender, enabling the consolidation and perpetuation of Japanese rule over northeast Asia. This study sheds light on a poorly understood aspect of Japanese wartime history: the importance of opium to social management, military encroachment, and imperial legitimacy in Manchuria. It also contributes to the field of global history, using drugs, goods that traverse and transgress all national boundaries, to integrate the study of the Japanese empire into the larger history of the early twentieth-century world. Finally, my model of the social anatomy of an urban drug economy may be useful to social scientists working on both historical and contemporary problems of commodities and power.