The herbal mixtures, Essiac™ and Flor‐Essence™, are sold as nutritional supplements and used by patients to treat chronic conditions, particularly cancer. Evidence of anticancer activity for the herbal teas is limited to anecdotal reports recorded for some 40 years in Canada. Individual case reports suggest that the tea improves quality of life, alleviates pain, and in some cases, impacts cancer progression among cancer patients. Experimental studies with individual herbs have shown evidence of biological activity including antioxidant, antioestrogenic, immunostimulant, antitumour, and antiocholeretic actions. However, research that demonstrates these positive effects in the experimental setting has not been translated to the clinical arena. Currently, no clinical studies of Essiac™ or Flor‐essence™ are published, but a clinical study is being planned at the British Columbia Cancer Agency by the University of Texas‐Center for Alternative Medicine (UT‐CAM) and Tzu‐Chi Institute for Complementary and Alternative Medicine. Copyright © 2000 John Wiley & Sons, Ltd.