Pupose : The Korean cancer pain assessment tool (K-CPAT) was developed in 2003 is consisted of questions concerning the pain location, quality of pain, present pain intensity, symptoms associated with pain, and psychosocial/spiritual pain assessments. This study was done to evaluate the reliability and validity of K-CPAT. Methods : A Stratified, proportional-quota, clustered, systematic sampling has been employed. Study population (903 cancer patients) was 1% of the target population (90,252 cancer patients). A total of 314 (34.8%) questionnaires have been collected. Results : Average pain score (5 Likert scale) by cancer type and at-present average pain score (VAS, $0{sim}10$) were correlated (r=0.56, P<0.0001), and showed a moderate agreement (kappa=0.364). Mean score of satisfaction was 3.8 ($1{sim}5$). The average time of completion of the questionnaire was 8.9 minutes. Conclusions: The K-CAPT is a reliable and valid instrument for the assessment of Cancer Pain for Korean.