The efficacy and QOL in a cancer pain patient who converted to transdermal fentanyl from low-dose morphine (n=5) or high-dose morphine (n=5) were retrospectively compared. Cancer pain control was evaluated by visual analogue scales (VAS) score. Patients switched from low-dose morphine demonstrated significantly better scales. The number of morphine rescues was also significantly less in the low-dose conversion group. In conclusion, conversion from low-dose morphine is useful for cancer pain control from the aspect of efficacy and QOL.