PURPOSE: The purpose of the study is to investigate the degree of fatigue and its related factors in patients with breast cancer. METHOD: The subjects of this study consisted of 62 breast cancer patients receiving chemotherapy. The Revised Piper Fatigue Scale, Disruption of Usual Activity Scale, Linear Analogue Self Assessment Scale and Self-Care Diary Scale were employed to measure fatigue, disruption of usual activity, mood state and physical symptom respectively. Collected data were analyzed using SPSS-PC to obtain summary statistics for the descriptive analysis, Pearson Correlation, and Stepwise Multiple Regression. RESULT: The results are as follows. 1. The mean score of the degree of fatigue was 4.82 points indicating moderate level. 2. The mean score of the degree of disruption of usual activity, mood state and physical symptom were 2.66, 5.00, and 4.69 points. 3. Fatigue of the subjects was significantly correlated with disruption of usual activity(r=.517, p<.01), mood state(r=.420, p<.01) and physical symptom(r=.463, p<.01). 4. With the result of stepwise multiple regression, disruption of usual activity, mood state and physical symptom being the three variables which could explain fatigue by 39.1%. The results of this study suggest that comprehensive intervention strategy for fatigue should be developed to maintain quality of life during and following chemotherapy considering these factors.