Abstract： Objective To evaluate the chemopreventive effects of boswellic acid and curcumin on 7,12-dimethyl benzanthracene (DMBA)-induced oral carcinogenesis in the hamster cheek pouch model.Methods Male Syrian golden hamsters(6-8 weeks old,80-130 g in weight) were randomly divided into seven groups,with group A serving as the untreated negative control.The left cheek pouch of the remaining hamsters was topically treated with 0.5％ DMBA in mineral oil three times a week for 6 weeks.They were then randomized to six groups with group B serving as a positive control and receiving no further treatment.Groups C-G were treated topically with 5,10 mg/L boswellic acid,5,10 μ moL/L curcumin,or the combination of 5 mg/L boswellic acid and 5 μmnol/L curcumin three times per week for 18 weeks.The animals were injected with bromodeoxyuridine intraperitoneally at 50 mg/kg 2 h prior to killing.At the 25 th week all the hamsters were sacrificed and cheek pouch tissue was harvested.One half of the tissue was snap frozen in liquid nitrogen for analysis of arachidonic acid metabolites,and the other half was fixed in 10％ phosphate-buffered saline(PBS)-buffered formalin for histopathological examination.Results Six-weeks of DMBA followed by 18-weeks of topical application of boswellic acid and curcumin,both boswellic acid (5,10 mg/L) and curcumin (5,10 μmol/L) significantly inhibited the incidence from 93.8％ to 73.9％ (P＞0.05),numbers from 2.19 ± 0.98 to 1.13 ± 0.81 (P ＜ 0.01) and size of visible tumors.Microscopically the incidence of squamous cell carcinoma and BrdU index were also significantly suppressed by boswellic acid and curcumin.Conclusions Both boswellic acid and curcumin were effective in preventing oral carcinogenesis in DMBA-induced hamster cheek pouch model.