The research described in this article was conducted in the Riverside District Health Authority in West London, an area where poverty exists alongside wealth. Demographic characteristics of the area were gathered including unemployment, housing conditions and homelessness, suicide levels, and incidence of HIV infection. The pattern of drug use included a wide range of illicit drugs; in addition, a broad spectrum of licit drugs were sold to illicit drug users on the black market, most of which were obtained from general practitioners who were prescribing to drug users and from non-drug users who had prescribed the drugs. The area was a center for drug dealing, much of which was conducted behind closed doors in private homes and pubs. The researchers were able to chart a hierarchy of drug dealers based on their observations. As a result of increased police harassment in the area, a more open street scene began to develop; the dealers' level of visibility depended on police movements in the locality. Qualitative data is instrumental when combined with quantitative data to form relevant and appropriate responses and to develop interventions aimed at reducing drug use and minimizing the spread of HIV infection. 7 references.