Eighty young adult male and female Syrian golden hamsters (Mesocricetus auratus) were divided into 4 equal experimental groups. In group I animals the left buccal pouch was painted three times weekly with a 0.5% solution of 7,12-dimethylbenz[a]anthracene (DMBA) in heavy mineral oil. In group 2 animals the left buccal pouch was similarly painted with DMBA, but the animals also received orally 10 mg vitamin E (dl-alpha-tocopherol) in peanut oil twice weekly on alternate days with DMBA painting. Group 1 animals received a similar amount of peanut oil vehicle, group 3 animals received only vitamin E (vitamin E controls) in peanut oil, and group 4 animals served as untreated controls receiving only peanut oil. Four animals in each group (2 males and 2 females) were killed at 8, 10, 12, 14, and 16 weeks. Buccal pouches were photographed and excised, and tumors were noted and measured in the left buccal pouches. In group 2 animals receiving vitamin E, tumor formation was significantly delayed, so that by 14-16 weeks there were fewer tumors and their average size was smaller than that of tumors in group 1 animals that were painted with DMBA but received no vitamin E supplement. In group 2 there was also less invasion of underlying tissues and less surface necrosis.