Chewing tobacco and snuff are the two main forms of smokeless tobacco in use in the United States. The prototypes of the person chewing tobacco were the baseball player (or coach) and the cowboy with a chew of tobacco in his cheek.
Cancers of the oral cavity (i.e., the mouth, lip, and tongue) have been associated with the use of chewing tobacco as well as snuff. Studies indicate that the tumors often arise at the site of placement of the tobacco.
Smokeless tobacco was formally classified as a "known human carcinogen" by the US government in 2000.