The Functional Assessment of Cancer Therapy-Prostate (FACT-P) questionnaire is a relevant, worldwide tool used for assessing the health-related quality of life in men with prostate cancer. The purpose of this study was to translate the FACT-P into Korean, to assess its reliability and validity, and to test its discriminative ability between the cancer patients and normal controls. The Korean version was developed via the FACT multilingual translation project. The translated questionnaire was self-administered to 70 prostate cancer patients and 70 age-matched controls. In evaluating its psychometric properties for cancer patients, internal consistency and test-retest reliability were used. Validity was estimated by using inter-subscale correlations and discriminant validity between cancer patients and controls. Cronbach's alpha coefficient for the individual subscales were 0.7 or greater (range 0.73 to 0.89), except for emotional well-being (0.61). The test-retest reliability showed high correlations (intraclass coefficients ranged from 0.72 to 0.93). Inter-subscale correlations demonstrated each subscale was unrelated, but moderate correlation was observed between social/family well-being and functional well-being subscales (r=0.56). The FACT-P scale could discriminate reliably between the cancer patients and controls in most subscales. In conclusion, the Korean version of the FACT-P is a reliable and valid questionnaire in patients with prostate cancer.