An estimated 69 000 people die each year from opioid overdose. Opioid overdose is easily reversed with the opioid antidote naloxone and with basic life support. Such care is generally only available in medical settings, however. These guidelines recommend that people who are likely to witness an opioid overdose, including people who use opioids, and their family and friends should be given access to naloxone and training in its use so that they can respond to opioid overdose in an emergency if a medical response is not available. Naloxone can be injected or administered intra-nasally and has minimal effects in people who have not used opioids. While naloxone administered by bystanders is a potentially life-saving emergency interim response to opioid overdose, it should not be seen as a replacement for comprehensive medical care.