The objective of this study was to evaluate the scientific evidence on the safety and efficacy of Essiac. This review serves as a clinical support tool. Electronic searches were conducted in 10 databases, 20 additional journals (not indexed in common databases), and bibliographies from 50 selected secondary references. No restrictions were placed on the language or quality of the publications. Standardized inclusion and exclusion criteria were used for selection. A review of the literature on Essiac and essiac formulations showed a lack of high-quality clinical trials to substantiate any of Essiac's traditional uses. Weak evidence from preclinical, animal, and laboratory data warranted a discussion regarding Essiac's use for cancer, but the results are inconclusive. Several other essiac preparations are noted in the literature, adding confusion to the exact formula and its proposed benefits. In general, there is a lack of both safety and efficacy data for Essiac and essiac formulations. Well-designed trials testing Essiac or individual herbal components are necessary to make firm recommendations.