Average heterozygosities for four communities (Savoonga and Gambell on St Lawrence Island, the King Island community now located in Nome, and Wales) are computed from blood allele frequencies. No significant relationship is found between this measure of heterozygosity and the amount of European admixture calculated from gamma globulin haplotype frequencies, indicating that forces other than European gene flow are affecting relative heterozygosity. However, within the two villages on St Lawrence Island, admixed individuals as a group have significantly higher average heterozygosity than non-admixed individuals. These results suggest that European gene flow significantly increases population heterozygosity when examined from a micro-populational or individual level, but may be obscured by other factors when several different populations are compared. This is probably because inter-village variation in admixture proportions, which range from zero to 8%, is small.