Fatigue, which may well be the most common experience of patients with cancer, remains underappreciated by health care professionals. Perhaps one reason is that because of its complexity and many components, fatigue is not completely understood. Knowledge of fatigue models, such as the integrated Fatigue Model of Piper, can help dietitians identify potential causes of fatigue such as activity-rest patterns, and identification can lead dietitians to early intervention. Understanding cancer treatment factors, such as nausea and decreased participation in activities of daily living, that are believed to play a part in fatigue form another level on which dietitians can provide intervention. Through intervention, dietitians, working with patients and other members of the multidisciplinary team, may increase the understanding and appreciation of fatigue as well as provide relief from it. Efforts to maintain nutritional status can decrease or prevent some of the fatigue associated with cancer and its treatment. Therefore, the goal of clinical dietitians who work with a fatigued patient with cancer is to use nutrition management to minimize therapeutic side effects and maximize the patient's nutritional parameters.