This article is a review of the status of biologically based complementary and alternative medicine (CAM) therapies that have potential anticancer activity with a focus on those agents that may be active in childhood cancer. The review presented in 2 parts includes the descriptions of the mechanisms that underlie their effects, the manner by which these agents are identified and evaluated and discussion of some of the limitations of current research. The first part introduces the topic of biologically based CAM therapies. The discussion includes a description the discovery biologically based products for cancer, the classification of these compounds and their use from the perspectives of the Ayurvedic and traditional Chinese medicine systems. Issues associated with evidence-based research of compounds used in these practices are addressed. The second part focuses on preclinical and clinical studies of specific herbs or natural products and their bioactive constituents that demonstrate potential in cancer therapeutics. Turmeric, mistletoe, green tea, ginseng, mushrooms, and micronutrients are representative of compounds that exert their effects through mechanisms attributed to specific chemical classes. The section concludes with a discussion of status of clinical trials of biologically based CAM therapeutics for cancer and the future direction of research.