Purpose: The purpose of this study was to identify the relationship of fatigue and functional status in patients with cancer. Method: The data were collected from August, 15 to October, 10, 2005. The subjects were recruited from three university hospitals and two general hospitals in B, U, and S cities in Korea. Fatigue was measured using the Fatigue Scale for Cancer Patients, and Functional Status was measured using the Karnofsky Performance Status Index. Result: 1) The mean score of fatigue was $79.72{pm}21.25$(range: 26-130), and the mean score of functional status was $79.33{pm}13.02$. 2) There were significant differences in the scores of fatigue by sex, age, marital status, employment, major care-giver, pain, and period after diagnosis. 3) There were significant differences in the scores of functional status by employment, major care-giver, pain, stage of cancer, period after diagnosis, and type of cancer. 4) There was a significant negative correlation between fatigue and functional status (r= -.472, p= .000). Conclusion: Increase in fatigue was associated with decrease in functional status in patients with cancer. Nurses must assess fatigue and functional status when caring for the cancer patients, and provide nursing intervention to relieve fatigue and to improve functional status.