C polymorphism of chromosomes 1, 9 and 16 was studied in 447 Mongoloids of Central Asia living under different ecological conditions; two highland (Kirghiz) and three steppe (Kazakh, Mongolian, and Dungan) populations. C band sizes were estimated according to the semiquantitative 5-level method of Patil and Lubs (1977). All the ethnic groups studied showed statistically significant homogeneity in the frequency of C variants. It is suggested that chromosomal C-heterochromatin material has no selective value in the process of human adaptation to extreme high-altitude factors.