| Inclusion criteria |
| Aged 20 years or older |
| Complaining of chronic pain |
| Inadequate pain control despite previous treatment (e.g., tramadol, codeine, oral morphine, oxycodone) |
| Ability to complete the questionnaire judged by the investigator |
| Provision of written informed consent form |
| Exclusion criteria |
| Experience of treatment with fentanyl matrix within the past 4 weeks |
| Current or past history of drug or alcohol abuse |
| Likely to complain of pain more than necessary for actual pain on account of, e.g., traffic accident insurance |
| Cannot use transdermal analgesics due to skin disease |
| Serious mental disease |
| History of hypersensitivity to opioid analgesics |
| Chronic lung disease or respiratory failure |
| Pregnant or possibly pregnant |
| Considered by the investigator to be ineligible to participate in this study based on warning, precaution, and contraindication in the package insert of fentanyl matrix |
| Considered by the investigator to be in a condition to threaten the patient's well-being |
