A case-control study of cancer of the oral tongue and floor of mouth was conducted in Kerala, Southern India, on 228 cases and 453 hospital-based controls, matched for age, sex and religion. We studied pan(betel)-tobacco-chewing, bidi (local type of cigarette)-and-cigarette-smoking, alcohol-drinking and snuff use, for their associations with risk, in males. Among females, only pan-tobacco-chewing was analyzed, as very few females indulged in the other habits. In males, a significantly increased risk was observed in association with pan-tobacco-chewing, bidi-smoking, bidi-plus-cigarette-smoking (but not cigarette-smoking alone) and alcohol-drinking (p less than 0.001 in all cases), although the effect of alcohol was no longer significant when adjusted for the other significant predisposing factors. Among females, pan-tobacco-chewing had a similar predisposing effect to that observed in males (p less than 0.001). In males an adjusted relative risk of 6.14 was associated with chewing 10 or more pan-tobacco quids per day (relative to those who never chewed). The corresponding relative risk in females was 9.27. In males, an adjusted relative risk of 7.46 was observed for those smoking 20 or more bidis per day (relative to never-smokers).