Anti-tumor B (ATB) is a Chinese herbal mixture of six plants (Sophora tonkinensis, Polygonum bistorta, Prunella vulgaris, Sonchus brachyotus, Dictamnus dasycarpus and Dioscorea bulbifera). ATB is also called Zeng Sheng Ping (ZSP). Previous studies have shown significant chemopreventive efficacy of ATB against human esophageal cancer, mostly squamous cell carcinomas. The chemopreventive effects of ATB on the development of 4-nitroquinoline-1-oxide (4NQO) induced oral squamous cell carcinomas in A/J mice were systematically evaluated and it was found that ATB reduced 4NQO-induced oral cancer development by approximately 60%. Similar results were also seen in 7,12-dimethylbenz(a)anthracene (DMBA) induced oral cancer in hamsters. A randomized clinical trial was conducted in patients with oral leukoplakia. Treatment with ATB (4 tablets, 3 times per day for 8—12 months) reduced the size of oral lesions in 68% of the patients versus 17% of the patients in the placebo control group (P < 0.01). These results indicate that ATB may be a potent chemopreventive agent against the development of oral cancer in humans.