In Hong Kong, the Central Registry of Drug Abuse (CRDA) is a register that forms the database for the study of drug addiction in the territory. Using a geographic information system-based approach, a pilot study was conducted, which integrated data from the CRDA, census, HIV (human immunodeficiency virus) reports/seroprevalence studies, and methadone clinics service statistics, to support the assessment of the trends of heroin addiction, HIV-related risks, and the inter-relationship with sociodemographic attributes in heroin users and the general population. Apart from the visualization of spatial distribution of heroin users, the study had uncovered specific local patterns at district levels. It is noted that despite a general decline in heroin addiction in Hong Kong, some areas showed a rising pattern in selected subpopulations. The increasing use of multidrugs also gave a district-specific pattern. Against the background of a low HIV prevalence in heroin users, the temporospatial pattern of injection provides potentially useful clues to track the spread of HIV risk. The location and coverage of methadone clinics, an important HIV-prevention strategy, were assessed in context of their public health impacts. It is concluded that the extension of the project to a long-term system would be useful for the study of addiction epidemiology, so that lessons learned from Hong Kong can contribute to the global knowledgebase on the development of effective response to substance abuse.