A new dosage strength of Duragesic® TTS patch was developed to deliver 12.5 micrograms of fentanyl per hour, which is considered to be equi-analgesic to a daily dose of 45 mg of morphine administered orally, and considered a safe starting dose in children aged 2 to 12 years. This is a single-arm, non-randomized, open-label, 15-day multicenter trial to determine the safety, clinical utility, and pharmacokinetics of Duragesic® in pediatric subjects who require treatment with a potent opioid for the management of continuous pain, allowing individual titration. After the 15-day primary treatment period, subjects may, at the investigator's discretion, continue long-term treatment with Duragesic® for a period of up to 1 year.