SummaryA participant observation study of the Piccadilly drug scene is described. A thriving market in diverted illicit drugs exists around this area, much of it an overspill from Drug Dependency Units and general practitioner prescribing. The economic organization of this market is described, the role of the dealers and runners, and the characteristics of the buyers. The nature and origins of the Piccadilly subculture are discussed, and its functional meaning. Public Health implications are also considered.