Until there is a cure for cancer and all surgeries and traumas can be prevented, opioids will continue to be a foundational tool available for the management of pain. Intravenous opioids are invaluable for patients with severe intractable pain, cancer pain, undergoing palliative/end-of-life care, and those unable to take medications enterally who require opioids for analgesia. This chapter will discuss indications, drug selection, adverse effects, pharmacokinetics, dosing, and method of administration for intravenous and subcutaneous opioid infusions.