Fentanyl transdermal matrix patch is a narcotic analgesic agent. Compared with the existing reservoir-type Durotep® Patch, fentanyl transdermal matrix patch is not liable to leakage of drug solution and does not contain alcohol, which becomes a cause of skin irritation. Also this new formulation has become available in a smaller dose of 12.5mg/hr while the smallest Durotep® Patch is 25mg/hr. While Durotep® Patch is currently indicated only for cancer pain in Japan, this clinical trial was planned to assess effectiveness, and safety of fentanyl transdermal matrix patch in Japanese patients with chronic intractable pain receiving codeine, morphine hydrochloride, or fentanyl injectable formulations. After pre-treatment period for seven to fourteen days for evaluating the eligibility of the patients for the study, patients will be treated for 4 weeks as Treatment period 1 and 48 weeks as Treatment period 2 followed by 3-day post-treatment observation period. One patch can be used for 72 hours, which is the same as the existing Patch. Starting from the first day of treatment, fentanyl will be applied to the chest, the upper arm or other appropriate site, which will be replaced with a new patch every three days (ca. 72 hr). Starting dose should be between 12.5 mcg/hr and 75 mcg/hr, depending on the prior opioid dose.