Aim. To investigate the calpastatin gene (CAST) polymorphism level and the genetic parameters of different productivity directions sheep populations, which are bred in the Ukraine southern region. Methods. Molecular genetics, population genetic. Results. Two allelic variants (M, N) and two genotypes (MM, MN) were found in animals of the Ascanian Fine-Fleeced, Ascanian Meat-and-Wool, Ascanian Karakul breeds and crosses of the Ascanian Fine-Fleeced with Texel (AFFxT) for the CAST gene. The frequency of allele M varies from 0.826 to 0.955, and allele N - from 0.045 to 0.174. Hence, in the environment of the studied sheep populations, homozygote MM prevails in frequency of manifestation. In the Ascanian Karakul and Romanov breeds, a rare NN genotype was identified, the carriers of which were 2.2 and 4.1% of animals, respectively. According to the genetic distance index, the sheep of the Ascanian Fine-Fleeced and Romanov breeds (d = 0.004), the Ascanian Meat-and-Wool and crossbred animals (AFFxT) (d = 0.005), the Ascanian Fine-Fleeced and Ascanian Karakul breeds (d = 0.007) turned out to be the most similar to each other. Conclusions. The polymorphism of the calpastatin gene in the gene pools of different origins sheep and productivity directions was studied, and it was found that individual populations have certain differences in the CAST locus polymorphism level and in the population genetic parameters used in the analysis. In particular, the relatively high level of heterozygosity (H = 0.273-0.287) and the number of effectively acting alleles (Na = 1.37-1.40) are characteristic of the populations of the Ascanian Karakul, Ascanian Fine-Fleeced and Romanov breeds. They are significantly inferior to the group of Meat-and-Wool and crossbreed (H = 0.080-0.095; Na = 1.09-1.10) sheep. Hence, a similar dependence is observed for other parameters. That is, in general, the calpastatin gene objectively reflects the nature of phylogenetic relationships between the studied gene pools.