OBJECTIVES: First the investigators want to determine if methadone is effective and safe for the treatment of neuropathic pain. Since a placebo control group would be unethical, the proposed comparator will consist of the "gold standard" conventional treatment, controlled release morphine. The investigators will compare methadone to controlled-release morphine with regard to how it affects the level of pain and extent of side effects. Next the investigators want to examine safety as well as to determine whether methadone leads to improvements in physical and emotional functioning, and participants' satisfaction with the treatment.