Purpose: We report two patients receiving high doses of systemic opioids in whom gradual switching of the opioid administration route from systemic to intrathecal provided satisfactory pain relief without excessive sedation or withdrawal symptoms. Case reports: In one of the patients, who was already receiving 500mg morphine intravenously but still suffered from right upper quadrant pain, it was difficult to increase the opioid dosage according to the WHO guidelines because of intolerable side effects. The other patient, in spite of taking a combination of systemic opioids equivalent to 760mg oral morphine, had inadequate pain relief and could not continue receiving home medical care. In both cases we could successfully change from systemic to intrathecal opioid administration in a step-wise manner without deterioration of pain control, adverse effects due to over dosage, or withdrawal symptoms. Intrathecal opioid administration also reduced drowsiness and improved daily activity. Conclusion: Currently, there are no guidelines for change of route of opioid administration from systemic to intrathecal administration and few published reports have concretely documented opioid route switching in Japan. A carefully planned, step-wise switching of opioid administration route from systemic to intrathecal should be considered in patients who are already taking high doses of systemic opioids. Palliat Care Res 2009; 4(1): 317-320