Oral squamous cell carcinoma, the fifth most common cancer worldwide, is a major cause of morbidity and mortality in India. The effect of lifestyle factors, including tobacco chewing, smoking and alcohol drinking, diet and dental care, on the risk of oral cancer was investigated in a case-control study conducted in Rajah Muthiah Dental College and Hospital, Annamalainagar, Annamalai University, Chidambaram, Tamil Nadu, India during the period 1991-2003. The study included 388 oral squamous cell carcinoma cases and an equal number (388) of age and sex-matched controls. All participants were interviewed using a structured questionnaire that contained data on demographic factors, family history of cancer, tobacco habits, use of alcohol, frequency, duration, cessation of these habits, dietary practices and oral hygiene. The data were analysed using multiple logistic regression model. Among people with chewing habits, those who chewed betel quid with tobacco [odds ratio (OR) 3.19, 95% confidence interval (CI): 0.48-2.13] and tobacco alone (OR 2.89) showed a greater risk than controls. Bidi smoking (OR 4.63) and alcohol drinking (OR 1.65) emerged as significant risk factors for oral cancer. These three habits showed increasing risk with increasing frequency and increase in duration of habits. Addition of alcohol to other habits also enhanced the risk for oral cancer. The combination of chewing and smoking together with alcohol drinking showed very high relative risk (OR 11.34). A positive association was observed between non-vegetarian diet, poor oral hygiene and poor dentition with the risk of oral squamous cell carcinoma. The fact that these risk factors are modifiable emphasizes the need for increasing awareness among the general public and policy makers as a first step in the prevention and control of oral squamous cell carcinoma.