This study was designed to evaluate the utility of transdermal fentanyl (transdermal fentanyl, TDF) for the treatment of pain due to osteoarthritis (osteoarthritis, OA) of the knee and hip, which was not adequately controlled by nonopioid analgesics or weak opioids. WOMAC is a reliable, valid, and responsive multidimensional, self-administrated outcome measure designed specifically to evaluate patients with OA of the knee or hip. TDF significantly increased pain control and improved functioning and quality of life. Metoclopramide appeared to be of limited value in preventing nausea and vomiting.