This chapter argues that social workers have an important role to play in supporting people with substance use problems, in collaboration with a range of other workers. It describes the conditions of problematic substance use in the Scottish context, and proceeds to discuss relevant policy and legislation. The chapter addresses some of the literature that explores the role of social work in this domain. It discusses the impact of austerity on service delivery; the lack of appropriate training; substance misuse, families and children; and other themes and challenges. The chapter concludes by making some suggestions about future directions. Problematic substance use in Scotland impacts on people's lives in terms of financial hardship; housing difficulties and homelessness; poor physical, mental, emotional and spiritual health; crime; social tensions; and stigma. The spread of intravenous heroin use in the 1980s and the associated HIV crisis led to a harm-reduction approach to tackling drug use.