Blood groups represent qualitative characteristics of humans which are controlled by one or a few genetic loci and due to this it is easy to determine various kinds of alleles and their frequencies in certain samples. Analyzing variability of characteristics such as blood groups, it is possible to get an insight in genetic structure of a population and it represents a suitable manner for detecting similarities and differences between populations. The intention of this study was to determine the genetic structure of the population of South Backa in a classic manner by phenotypic characteristics in MNSs blood group system, to assess frequencies of alleles, phenotypes, genotypes, allelic frequencies and genetic distances between the population of South Backa and populations of various geographic regions. Immunohematologic investigation of 1.000 persons included blood group testing in the MNSs system, which was a basis for applying population-genetic analysis based on Hardy-Weinberg equilibrium in populations. Results of investigation revealed that in population of South Backa, s allele has the highest frequence (85.59%); the most frequent genotypes are ss (48.5%), MN (43.4%), Ss (37.4%); the most frequent phenotypes are MNss (19.3%), MNSs (18.4%) and NNss (15.3%). Genetic distances between populations are greatest among geographically most distant populations as Eskimos, Australian Aborigines, populations of Papua-Gvinea, Fiji and low in populations of Turkey, Italy, Albania and Cyprus.