Histopathological effects of chewing of betel quid with tobacco was studied by simulating four different chewing habits, using mouse glandular stomach mucosa as a model system. Chronic oral administration for five months resulted in marked intestinal metaplasia in all animals receiving extract of tobacco with betel nut and lime and extract of tobacco with betel leaf, nut and lime, in doses normally ingested by human addicts. Tobacco markedly augmented the effect of other ingredients. Lime and Piper betle L. var. bangla probably played a protectant role by reducing the dysplasia and metaplasia. In the light of the growing use of smokeless tobacco and betel chewing habits, our results may exemplify the way in which the various chewing mixtures, which are ingested daily in relatively large quantities, could affect carcinogenesis in habitual chewers.