The inhibitory effect of dietary supplementation with flavonol quercetin on 7,12-dimethylbenz[α]anthracene (DMBA)-induced hamster buccal pouch carcinogenesis was investigated. Dietary quercetin inhibited the incidence of both papillomas and tumors induced by DMBA. The fluorescence spectra of papillomas and tumors showed different prominent maxima and a characteristic peak around 620-630nm, which could be attributed to the accumulation of porphyrin compounds. Further, the fluorescence intensities at 630 nm (FI630nm) were elevated, whereas the ratio FI520nm/FI630nm was decreased in DMBA-induced lesions. Quercetin treatment significantly decreased FI630nm and increased the ratio FI520nm/FI630nm when compared with DMBA-induced lesions. It is therefore evident that quercetin has an inhibitory effect on DMBA-induced carcinogenesis and further studies will throw more light on its use as a chemopreventive agent against oral cancer.