Melanoma is on the rise in Canada. High-dose interferon (HD IFN) is the only proven option for melanoma at high risk of recurring. This drug is costly, has significant toxicity, a long duration of administration and at best, a small survival benefit. Within the peer reviewed literature, little is known about the management and outcomes of melanoma in Ontario, or Canada. As the first step to address this, we propose a population study of HD IFN. The purpose of this study is to investigate the toxicity (risks) and effectiveness (benefits) of HD IFN when utilized in the population of Ontario. This study will be undertaken using extensive electronic health information covering the whole province of Ontario. We predict that results from this project will provide incentives to reduce use of HD IFN by identifying evidence of limited population-based effectiveness and significant toxicity of HD IFN. Such a reduction in use would improve health system sustainability and avoid unnecessary drug toxicity in Ontario, and Canada.