PRLR gene has been studied as a candidate gene for litter size in swine because of prolactin biological functions and their association with reproduction. Prolactin receptor gene is mapped on porcine chromosome 16. The established PCR-RFLP polymorphism at PRLR locus demonstrated the presence of two alleles, А and В and three genotypes АА, АВ and ВВ. There were found different allele and genotype frequencies in different pig populations with variation of the effects of PRLR genotypes on litter traits. Additional studies should be done in specific breeds and populations to evaluate the association of existing PRLR locus polymorphism with reproductive traits before application of marker-assisted selection in these populations.