Substance use costs British Columbia $4.9 billion in 2014, of which 70% was due to alcohol and tobacco. These estimates include costs related to the use of health care resources, productivity losses, criminal justice, and other direct costs such as accidents, research and prevention. Broader societal costs not included in these estimates relate to inequities, marginalization and hindered social development. This project aims to develop a model to evaluate the economic and social impact of legal substance use harm prevention in British Columbia. Evidence on economic consequences and how public health programs can minimize costs and harms from substance use is important for policy makers, who need to consider the health system priorities against efficiency, scalability and sustainability of interventions. The challenges to developing comprehensive economic evaluations in public health are well known. In the area of substance use, these pertain to the multitude of the socioeconomic determinants that influence use - such as employment, income, social exclusion, and hopelessness - and the difficulty of measuring broader benefits including family wellbeing, community development and equity gains. This fellowship will facilitate collaboration between knowledge users and academics with the aim of optimizing investment in the area of alcohol, tobacco and cannabis harm prevention in BC. It will provide the Ministry of Health with tools to implement efficient priority setting that aligns with the institution's values and development goals. This will be achieved through important methodological advances to allow evaluations to account for the broader societal impact of preventing harm from legal substance use in BC. As a result, this fellowship will sustain future research in health economics with an increased ability to respond to policy makers' needs when it comes to priority setting.