We herein describe the development and validation of the Cancer Fatigue Scale (CFS) for assessment of fatigue in cancer patients. We designed this scale specifically to reflect the nature of fatigue experienced by cancer patients, by using factor analysis; the CFS is a 15-item scale composed of 3 subscales (physical, affective, and cognitive subscales). Three hundred seven cancer patients participated in the validation phase. Construct validity, confirmed by repeating factor analysis, was good. Convergent validity, confirmed by a correlation between CFS and a visual analogue scale for fatigue, was also shown to be good (r = 0.67, P < 0.001). The CFS had good stability (average test-retest reliability r = 0.69, P < 0.001) and good internal consistency (Cronbach's alpha coefficient for all 15 items = 0.88). The present study indicates that the CFS is a brief, valid, and feasible measure of fatigue for use with cancer patients.