Studies in pediatric oncology have shown a positive effect of physical activity on disease-and treatment-related side effects. Although several reviews have approved the benefits of therapeutic exercise for adult cancer patients, no systematic review exists summarizing the evidence of physical activity in pediatric oncology. We identified a total of 17 studies using the PubMed database and Cochrane library. To evaluate the evidence, we used the evaluation system of the Oxford Center for Evidence-Based Medicine 2001. The findings confirm that clinical exercise interventions are feasible and safe, especially with acute lymphoblastic leukemia (ALL) patients and during medical treatment. No adverse effects have been reported. Positive effects were found on fatigue, strength, and quality of life. Single studies present positive effects on the immune system, body composition, sleep, activity levels, and various aspects of physical functioning. Child-specific aspects such as cognitive abilities, growth, adolescence, and reintegration into peer-groups, school, and sports have barely been taken into consideration. The evidence for exercise interventions in pediatric oncology is rated level "3. " Although the results are very promising, future research of high methodological quality and focusing on child-specific aspects is needed to establish evidence-based exercise recommendations, particularly for childhood cancer patients.A s a result of improved treatment regimes in pediatric oncology, the survival rates of children with cancer have risen to ~80% for 5-y survival (1-4). Therefore, the population of childhood cancer survivors is constantly growing. Despite these positive developments, childhood cancer is associated with a wide spectrum of various disease-and treatment-related side effects that may develop into chronic diseases and therefore result in long-term consequences. A negative impact on social, psychological, and physiological levels can be observed. Inactivity (5-7), impaired cardiopulmonary and musculoskeletal function, as well as reduced motor performance levels (8,9) and cognitive abilities (10) have been detected. Current studies also examined a negative impact on psychological well-being, satisfaction, and social functioning (11). Taken together, an impaired quality of life can thus be determined (8,12).During the past few years, several studies have generated first hints describing holistic, positive effects of clinical exercise interventions in pediatric oncology. First results present an association between increased physical activity levels in childhood cancer patients and an improvement in quality of life (13). In particular, physical functioning is increased, anxiety is reduced, and social integration is encouraged (14). Considering the fact that physical activity plays a vital role in the physiological and psychosocial development of children, therapeutic exercise in pediatric oncology is particularly important. However, there is still a lack of comprehensive and evidence-based data in the field o...