This research project employs a multi-site, multi-method approach to understanding retail heroin markets from a public health perspective. Key topics of investigation include: (1) a comparison of the characteristics of street heroin markets in 6 areas of Melbourne; (2) an examination of the dynamics of these markets and their relationship to health outcomes; and (3) identification of the relationships between market characteristics, consumer behaviour and health outcomes. This research provides an improved understanding of the public health implications of retail heroin markets through examination of the dynamic interaction of the various processes that constitute these markets. It will lead to recommendations for the management/regulation of heroin-related health problems.