question: Opioid misuse is common, as is opioid agonist treatment of opioid dependence. Almost 3% of Australians and over 3.5% of those living in New Zealand report misuse of analgesics. Over 50,000 Australians receive opioid agonist treatment with methadone or buprenorphine for management of severe opioid use disorder.The perioperative period is an opportunity to identify pre-existing opioid misuse, and to introduce interventions to reduce the risk of development of opioid use disorder. Challenges of acute perioperative pain management or intensive care management of patients receiving opioid agonist treatment include opioid tolerance and ongoing prescribing of methadone or buprenorphine. There has been some ambiguity about the optimal perioperative management of buprenorphine, a partial agonist at the mu receptor.In this article, a framework to identify emerging opioid misuse problems, identify risk of overdose and to manage the opioid-dependent patient on opioid agonist treatment perioperatively or in the intensive care unit is provided. Diagnostic criteria and risk stratification criteria are presented. Management strategies include trauma-informed care, care planning and care coordination with community practitioners and opioid agonist treatment providers. Continuing methadone or buprenorphine perioperatively with additional opioid and non-opioid analgesia is generally recommended. Increased opioid agonist treatment doses may be required on discharge. An algorithm for decisions about opioid agonist treatment management in the intensive care unit based on the risks of opioid withdrawal and toxicity is considered. Strategies for managing the opioid-dependent patient who is not in treatment are also discussed.