Background: The high prevalence of betel quid chewing is associated with a serious burden of oral diseases. However, there is limitertd research on the effects of betel quid, smoking, and alcohol on oral cancer in the Hunan province, China. Objectives: We investigated the relationship between oral cancer and betel quid chewing, smoking, and alcohol consumption in the betel quid endemic area of Hunan province. Methods: A paired case-control study from January 2014 to September 2015 was conducted in the Hunan province, China. We recruited 304 ora...