Анотация: In order to determine the allele and genotype frequencies for the polymorphism of the gene coding the C3 component of the complement system, 432 sheep from nine breeds of different productive types were studied. Tests were carried out with Mouton Charollais, Ile de France, Trakia Merino breeds, milk crosses [Stara Zagora x East Friesian and (Stara Zagora x East Friesian) x Pleven Blackhead], White Maritsa, Patch-faced Maritsa, Karnobat, Pleven Blackhead and Stara Zagora breeds, with 48 animals studied from each breed. The animals were reared at the Agricultural Institute - Stara Zagora, the Agricultural Institute - Karnobat and private farms. Seven alleles were discovered (S, S1, S5, S7, S10, F, and F1), forming nine genotypes (SS, SS1, FS, FS5, FS7, FS10, FF, FF1, F1F1). The S allele frequency was the highest in sheep from the Stara Zagora and Trakia Merino breeds. In all other breeds, most common was the F allele, with this tendency being most evident in the Mouton Charollais and Pleven Blackhead breeds. The very rare S1 allele was found in three breeds with a frequency of 0.01 to 0.05. Another rare allele discovered over the course of his study was F1, with frequency varying between 0.2 and 0.13. The frequencies of the nine established genotypes (SS, SS1, FS, FS5, FS7, FS10, FF, FF1, F1F1) varied in each breed. The SS genotype was most commonly encountered in the Stara Zagora breed (0.42), the heterozygous FS genotype was most common in the Mouton Charollais breed and milk crosses (0.23), whereas the animals homozygous for the F allele were prevalent among the Pleven Blackhead breed (0.54). The heterozygous FS5 genotype was also notable, having a frequency of 0.33 in the Karnobat breed