The history of opium is a major theme in modern Chinese history. Books and academic careers have been devoted to its study. Yet the question that scholars of the opium wars and of modern China have failed to ask is how the demand for opium was generated. My puzzle, during the initial stage of research, was who smoked opium and why. Neither Chinese nor non-Chinese scholars have written much about this, with the exception of Jonathan Spence. Although opium consumption is a well-acknowledged fact, the reasons for its prevalence have never been fully factored into the historiography of the opium wars and of modern China. Michael Greenberg has dwelt on the opium trade, Chang Hsin-pao and Peter Fay on the people and events that made armed conflicts between China and the West unavoidable. John Wong has continued to focus on imperialism, James Polachek on Chinese internal politics while Opium regimes: China, Britain, and Japan, 1839–1952, the latest work, has studied the political systems that controlled opium. But the political history of opium, like the opium trade and the theatre of war, is only part of the story. We need to distinguish them from the wider social and cultural life of opium in China. The vital questions are first, the point at which opium was transformed from a medicine to a luxury item and, secondly, why it became so popular and widespread after people discovered its recreational value. It is these questions that I address. We cannot fully understand the root problem of the opium wars and their role in the emergence of modern China until we can explain who was smoking opium and why they smoked it.