The frequency and polymorphism of erythrocyte G6Pd deficiency were studied in schoolchildren of Koby settlement, Apsheron district (n = 469). The total frequency of Gd- alleles was 3.6%. Out of 10 hemizygotes found 9 had Gd- alleles of the III class and 1 had Gd- allele of the II class. The mutant enzyme was isolated from 10 ml venous blood samples and studied according to WHO program. Three different mutant forms of G6PD were found, neither of them having been earlier described. One of these alleles was common for the population studied (n = 6).