Fatigue and impaired physical performance are common and sometimes serious problems of cancer patients during and after treatment. To avoid fatigue, cancer patients are often advised to rest and downregulate their daily activities. However, these recommendations can cause paradoxical results. Since inactivity induces muscular wasting, prolonged rest can result in further loss of endurance. Recent studies suggest that exercise, as well as behavioral and some psychosocial interventions, may reduce fatigue and improve the performance status of cancer patients. In this paper, we review interventions proposed for the treatment of cancer-related fatigue and present the results of a study about the effects of exercise on the physical performance of patients with hematological malignancies. Sixty-six inpatients (34 men, 32 women) undergoing conventional ( n=45) or high-dose chemotherapy with stem cell rescue ( n=21) for the treatment of a hematological malignancy exercised daily on a treadmill. Physical performance was assessed on admission and once a week during hospitalization (30+/-10 days, range 10-49). Physical performance remained unchanged in a submaximal standard stress test (on admission: 5.5+/-1.4 km/h; midhospitalization: 5.3+/-1.3 km/h; at discharge: 5.5+/-1.3 km/h; p=0.60) despite chemotherapy and its related complications. A significant decrease in the mean hemoglobin concentration (from 10.3+/-2.0 g/dl on admission to 9.6+/-1.2 g/dl at discharge; p=0.03). We conclude that a daily endurance-training program reduces the treatment-related loss of physical performance in patients with hematological malignancies undergoing chemotherapy.