More than twenty-five years after the first signs of potential harm, the US remains locked in the grip of an opioid epidemic, with more Americans dying from overdoses than ever before. 1 Diversion of prescription opioids plays an important role in opioid-related harms. Much of the scientific and public health focus on diversion has been on end-users, given how commonly non-medical prescription opioid use occurs, as well as the proportion of individuals who report that their source of non-medical opioids was friends or family. However, diversion of opioids, as well as their rampant oversupply, can be discerned higher up the supply chain, including among wholesalers, pharmacies and rogue prescribers whose behavior may trigger well-described "flags" warranting further evaluation and action.