Oral cancer is caused by chewing and smoking of tobacco. To assess the feasibility of primary prevention of oral cancer, two cohorts were studied in base-line surveys and then followed up annually for 10-yr in Ernakulam district of Kerala state. The intervention cohort consisted of 12212 tobacco users aged 15 yr and over, who were exposed to a concentrated program of education against tobacco use. The control cohort was a non-concurrent cohort of 6075 tobacco users studied using similar methods but with a minimal amount of advice against tobacco use. The stoppage of tobacco use increased and the incidence rate of leukoplakia decreased significantly and substantially in the intervention cohort compared to the control cohort. The decrease in the incidence of leukoplakia was indicative of the decrease in the risk of oral cancer since the two were intimately related. This study demonstrated feasibility of primary prevention of oral cancer.