This paper studies the origins and consequences of the opioid epidemic. Drawing on recently unsealed records from state litigation against Purdue Pharma, we exploit detailed features of the marketing of OxyContin, which initially targeted the cancer pain market, to assess the role of supply side factors and to instrument for the level of prescription opioids. We document a strong link between Purdue Pharma’s promotional targeting and future increases in the supply of prescription opioids and deaths from prescription opioids and all opioids. In terms of indirect effects we find that the epidemic triggered a large increase in disability and SNAP claims and was accompanied by worsening of infant health and increased non-marital fertility rates.