Appropriate pain assessment is very important for managing cancer pain. This study was designed to evaluate the utility of the Korean Cancer Pain Assessment Tool (KCPAT) by assessing changes in the management of cancer pain. The changes in pain intensity, the pattern of drug prescriptions, and the patients' satisfaction with pain control were analyzed after using the KCPAT. The results indicated that pain medicine prescriptions were changed in 194 (51.5%) cases after using the KCPAT, and 69.5% of these changes were affected by the KCPAT. After using the KCPAT, pain intensity as assessed by the Visual Analogue Scale (VAS, 0-10cm) decreased (4.31+/-2.35 vs. 3.60+/-2.45, P<0.0001), and the presence of associated symptoms and psychosocial items was significantly reduced. The patients' satisfaction with pain control was improved. Forty-four physicians (89.8%) thought that the KCPAT was useful. The KCPAT improved patients' satisfaction with pain control and was a useful tool for evaluating and managing cancer pain.