Introduction: Although fentanyl patch (FP) are often used to treat cancer pain because of the low incidence of adverse effects of this formulation, there are cases in which it is impossible to eliminate the pain despite increasing the doses. We report a patient of advanced gastric cancer with abdominal pain, in whom successful pain control was achieved by opioid rotation from FP to continuous intravenous infusion of morphine hydrochloride. Case Report: The patient was a male in his 60's who had been diagnosed as having primary gastric cancer and complained of abdominal pain, thought to be visceral pain caused by obstruction of the digestive tract. Oral intake became more difficult as the disease progressed. Despite a switch to FP from oxycodone used to treat the abdominal pain and an increase in the dose, pain relief was not achieved. Then, we undertook a partial opioid rotation to continuous intravenous infusion of morphine hydrochloride, which provided adequate pain control. Discussion: One possible reason for the pain relief in this patient is suppression of the gastrointestinal motility by morphine. When adequate pain relief cannot be achieved with one opioid, opioid rotation should be considered. We concluded that the opioid rotation should, however, be performed in a stepwise manner. Palliat Care Res 2009; 4(1): 307-311