In 2001, we made a dental anthropological survey of the Dai tribe, one of the Chinese minorities in Yuen Jian Province. Subjects were young adults of the tribe, which is historically from the Southeast Asian area. Dental impression models were collected from this population, and the frequencies of 22 dental traits were investigated. Results were compared with those of other Asian populations based on Turner's Mongoloid dental variation theory. Principal coordinate analysis based on Smith's mean measure of divergence using frequencies of the 17 traits suggested that the Dai tribe was included in the Sundadont group typical of Southeast Asians, but its position was close to the Sinodont group. The Dai tribe is said to have a close relationship to people in Thailand according to anthropological and linguistic studies. In light of these results and the estimated past and present distribution of Sinodonty and Sundadonty, we speculated that the Dai tribe in Yunnan Province was genetically similar to Thailand people who have Sundadont characters, but environmentally close to the Han tribe, the majority of the Chinese population, and other Sinodont tribes around them. These historical factors were thought to be reflected in their dental characteristics.