C ancer-related fatigue (CRF) has been operationally defined by the National Comprehensive Cancer Network (NCCN) as a “persistent, subjective sense of tiredness related to cancer or cancer treatment that interferes with usual functioning.”1(p309) In people with no known pathology or limitations, fatigue is a universal human experience that is regarded as a basic protective mechanism against the depletion of metabolic energy reserves. With adequate rest, nourishment, and sleep, fatigue in these individuals is self-limiting. However, in contrast to exercise-induced fatigue experienced by these individuals, the fatigue experienced by patients with cancer is of greater magnitude and persistence, tends to remain after rest periods, is more disruptive to activities of daily living, and has a more negative affective impact.2 Until recently, medical advice for patients undergoing treatment for cancer was to obtain additional rest and avoid activities that are physically challenging. Currently, the use of exercise as an adjunct therapy for cancer treatment-related symptoms has gained favor in oncology rehabilitation as a promising intervention.3 The purpose of this update is to examine evidence from recent (since 1997) randomized clinical trials (RCTs) regarding the effectiveness of exercise as an intervention for CRF. The sources of data included all those RCTs found from MEDLINE and CINAHL literature searches for the selected time period using the key words “exercise,” “fatigue,” and “cancer.” The effects of exercise on fatigue in patients with cancer, both those in intervention programs and survivors (5-year), are summarized in the Table. We present findings from 8 recent RCTs, 6 of which involved patients with breast cancer, and provide suggestions for exercise program protocols and for future research endeavors. The majority of articles in the literature involve patients with breast cancer, and physical therapists should take note of this point when making clinical judgments based on the …