Two-dimensional gel electrophoresis followed by silver-staining has been employed to study 59 red cell lysates for genetic variation in Cheju population. Forty-nine polypeptides selected without respect to variability were considered suitable for scoring. Of the total of 2,891 polypeptides, 98 exhibited the combination of a normal and a variant polypeptide. All variants were present in either the father or the mother of the subjects. The observed index of heterozygosity was 3.3%±0.23%. The heterozygosity in Korean (Cheju) population was compared with those in other populations.