Neuropathic pain is a chronic pain state produced by injury in the peripheral nerves or tissues. It has been shown that neuropathic pain is resistant to conventional analgesics including morphine. It is categorized into sympathetically maintained pain (SMP) and sympathetically independent pain (SIP), depending on sympathetic sensitivity. Frequently, even SMP may not be alleviated by sympathetic manipulation and antidepressants or anticonvulsants may not be effective in relieving neuropathic pain. The use of opioids is an alternative in these cases. It has to be regarded that the opioids have to be less tolerant but more effective in treating neuropathic pain. It is recommended that the opioids be coadministered with any other kind of effective agents in the circumstances where the opioids may produce any severe side effects. Activation of the endogenous opioid system is beneficial in relieving neuropathic pain. Since the effectiveness of opioids depends on many factors such as characteristics of pain, type of injury, routes of administration, time intervals between injury and treatment, etc. it is very important to choose the most appropriate treatment in relieving neuropathic pain.