This chapter explains opioids dose, side effects, and mechanism of action. Drug interactions of opioids (morphine, fentanyl, meperidine) are mentioned. Butorphanol, buprenorphine, pentazocine, nalbuphine are told as complex action opioid. Opioid antagonists and anesthetic management of an opioid addict is explained. Epidural and intrathecal use of opioids has been mentioned.