Illicit opiate addiction has emerged as a major problem in many Western countries in the second half of this century, and its social harm implications have become much exacerbated with the onset of the HIV epidemic in the 1980s. By now, most Western jurisdictions have resorted to methadone treatment as the most effective and best researched intervention against the negative consequences of opiate addiction including mortality, morbidity, crime, and loss of social functioning. Methadone treatment in Canada features a long, turbulent, and instructive history as an exemplary case study in public policy. While both Britain and the U.S. experimented with opiate prescription treatment in the first half of the century, Canadian proposals for such programs initially never made it beyond the discussion stage, largely due to the influential resistance from the law enforcement sector. However, in light of growing influence from an emerging addictions treatment sector, Canada became the first Western jurisdiction to experiment with methadone prescription for the treatment of opiate addiction forty years ago. Methadone treatment became quickly and widely established as an effective treatment modality through the 1960s. But in the early 1970s, resistance from the law and health sectors evolved, and triggered the government to establish a set of comprehensive and restrictive federal methadone treatment regulations, which have dominated its realities until today. Almost completely regulated out of existence by the end of the 1970s, methadone treatment's prevalence gradually increased again through the 1980s, and recent decentralization efforts to provincial levels earlier this decade have had dramatic effects on treatment availability. Significant events in the Canadian history of methadone treatment and its regulation reflect developments in the U.S., and substantial recent domestic treatment expansion developments--as well as renewed sparks of resistance--are reminiscent of methadone treatment's patterns of history as they developed in the late 1960s. This paper traces the turbulent history of methadone treatment, regulation and policy in Canada with particular attention to institutional, professional and political determinants at the complex intersection of health, law, and addiction.