Children with cancer frequently use complementary and alternative medicine (CAM), especially in conjunction with conventional therapy. Dietary supplements are a commonly used CAM modality, with the prevalence of supplement use ranging from 35% to 50% of children with cancer in surveys completed in the United States. Less is known about the use of dietary supplements in developing countries. The evidence for some dietary supplements providing some benefit to children with cancer is reviewed. Preliminary studies have shown that antioxidant status may affect chemotherapy tolerance in children with acute lymphoblastic leukemia. Other supplements, including TRAUMEEL S®, glutamine, vitamin E, Immunocal®, colostrum, and probiotics, may help to reduce gastrointestinal toxicities of chemotherapy and radiation. However, more definitive evidence is needed. Most dietary supplements have not been tested adequately to determine their safety and efficacy, with even less understood about their potential interactions with conventional chemotherapy and radiation. With the greater use of dietary supplements by patients with cancer, increasing scientific attention is being paid to the investigation of these therapies. But research on dietary supplements is complex and usually more difficult than that on conventional medications. Strong research designs are critical in obtaining information that will ultimately influence clinical practice and public awareness. Pediatr Blood Cancer 2008;50:490–493. © 2007 Wiley-Liss, Inc.