Children with cancer are using complementary and alternative medicine (CAM) to relieve symptoms, reduce side effects of treatment, and cope with the emotional aspects of having a life-threatening illness. Parental decisions about using CAM should be based on studies of efficacy and safety. Unfortunately, little evidence of efficacy is available for the majority of CAM therapies. This article discusses the methodological challenges to conducting CAM research in children and the evidence needed to support integrative medicine in pediatric oncology.