This paper examines the role of clinical practitioners and clinical researchers internationally in establishing the utility of harm-reduction approaches to substance use. It thus illustrates the potential for clinicians to play a pivotal role in health promoting structural interventions based on harm-reduction goals and public health models. Popular media images of drug use as uniformly damaging, and abstinence as the only acceptable goal of treatment, threaten to distort clinical care away from a basis in evidence, which shows that some ways of using drugs are far more harmful than others and that punitive approaches and insistence on total abstinence as the only goal of treatment often increases the harms of drug use rather than reducing drug use. Therefore the leadership and scientific authority of clinicians who understand the health impact of harm-reduction strategies is needed. Through a review of harm-reduction interventions in Canada, the United Kingdom, the United States, Australia, Switzerland, and the Netherlands, we identify three ways that clinicians have helped to achieve a paradigm shift from punitive approaches to harm-reduction principles in clinical care and in drug policy: (1) through clinical research to provide data establishing the effectiveness and feasibility of harm-reduction approaches, (2) by developing innovative clinical programmes that employ harm reduction, and thereby (3) changing the standard of care to include routine use of these evidence-based (but often misunderstood) approaches in their practices. We argue that through promotion of harm-reduction goals and methods, clinicians have unique opportunities to improve the health outcomes of vulnerable populations.