Aims. To indicate how the system of pharmaceutical regulation of the sale and use of opium in Great Britain continued throughout the first half of the 20th century. Design. An oral history investigation of community pharmacy in Great Britain (n=50), together with an analysis of standard pharmaceutical texts. Setting. Community pharmacies in Great Britain during the 20th century. Participants. Retired community pharmacists with experience of the sale and use of opium during the period. Measurements. Oral testimony of retired community pharmacists about the use and sale of opium, and quantitative analysis of numbers of official preparations of opium available during the period. Findings. The popular use of opium continued well after the First World War, and its use as an ingredient of prescribed medicines continued well beyond the introduction of the National Health Service in 1948. Conclusions. Although the role of pharmacy in the regulation of opiates and other drugs was displaced by medicine following the passage of dangerous drugs legislation in the 1920s, pharmacists continued to play an important part in this regulation, exercising considerable discretion in the process.