<jats:title>Abstract</jats:title> <jats:p>Fatigue is a highly prevalent condition among cancer patients. Although most cancer patients report that fatigue is a major obstacle to maintaining normal daily activities and quality of life, it is seldom assessed and treated in clinical practice. Few studies have explored its epidemiology, possible etiologies, or management. Cancer-related fatigue, which recently was accepted as a diagnosis in the International Classification of Diseases 10th Revision-Clinical Modification, reduces physical, psychological, and social functioning and results in significant distress for patients and caregivers. Adequate evaluation of fatigue must do more than simply assess severity. The assessment should clarify other characteristics, determine the degree to which fatigue interferes with the activities of daily living, and identify potential causes, including the underlying disease, disease treatments, intercurrent systemic disorders, psychological disorders, and other conditions. Possible primary therapies include modification of the patient's drug regimen, correction of metabolic abnormalities, and pharmacologic treatments for anemia (e.g., epoetin alfa), depression, or insomnia. Other symptomatic interventions include specific drug treatments, exercise, modification of activity and rest patterns, cognitive therapies, sleep hygiene approaches, and nutritional support. Pharmacologic approaches, which are supported by limited studies and growing clinical experience, include psychostimulant drugs, corticosteroids, and possibly other therapies. Although additional research is needed to further identify the causes and corresponding treatment of fatigue, practitioners should routinely assess and treat patients who may benefit from currently identified interventions, because fatigue can profoundly undermine the quality of life of patients with cancer.</jats:p>