Abstract: An anthropological research on 122 Lai people living in the Yunnan-Guizhou Plateau was carried out in 1988. The Lai people has attributed no definite ethnic group yet. Their ABO blood groups were determined. The A, B, O and AB phenatype frequencies of ABO blood groups in Lai people are 0.1721, 0. 4836, 0.2951 and 0.0492. The p, q and r gene frequencies of ABO blood groups in Lai people are 0.1189, 0.3201 and 0.5610. The |D/a| test according to Hardy-Weiberg's law is good.
The frequency of ABO blood groups in Lai people is obviously higher than that in the Han series, except the Northern Han series, and is very near to the Li people in Hainan lsland and Tai in Tailand. It is implied in this connexon that the Lai people has a close genetic relation with the Li people. Much work done by other authors on the ethnological aspects, cultural anthropology and archaeology has led to the conclusion that Lai tribe has a close racial relation with Li group and both groups may originate from a same ancester living in Southern China. This conclusion is confirmed by the results of our research.

Key words: Lai tribe; ABO blood groups; Gene frequency