Since the discovery of Gm ab3st haplotype which characterizes Mongoloid populations in 1966, the distribution of the genetic markers of immunoglobulins (Gm) among the Mongoloid populations scattered from Southeast Asia through East Asia to South America has been investigated and concluded as follows: 1) Mongoloid populations characterized by the four Gm haplotypes, ag, axg, ab3st and afb 1b3 are divided into two groups on the basis of analysis of genetic distances based on the Gm haplotype frequencies: one is a southern group characterized by a remarkably high frequency of Gm afb 1b3 and a low frequency of Gm ag and the other is a northern group characterized by a high frequency of Gm a and an extremely low frequency of Gm afb 1b3. 2) Populations in China, mainly Han including minority nationalities, show remarkable heterogeneities from north to south, in sharp contrast to Korean and Japanese populations showing homogeneities, respectively. The center of dispersion of the Gm afb 1b3 characterizing southern Mongoloids must exist in Guangxi and Yunnan area in the southwest China. 3) The Gm ab3st gene found in the highest incidence among the north Baikal Buriats flows in all directions. The gene, however, shows precipitous drop which occur from mainland China to Southeast Asia and from North to South-America, although the Gm ab3st gene is still found in high incidences among Eskimos, Yakuts, Tibetans, Olunchuns, Koreans, Japanese and Ainus. On the other hand, the gene is introduced into Huis, Uighurs, Indians, Iranians and far Hungarians.(ABSTRACT TRUNCATED AT 250 WORDS)