he aim of this research was to estimate Holstein’s allelic frequencies for Kappa casein gene in Nariño - Colombia. The genotype of each animal was molecularly determined by the PCR- SSCP technique on 748 Holstein animals, which were distributed in three dairy zones and 57 farms located in Pasto, Pupiales and Guachucal. Matrix data were analyzed t with the TFPGA (Tools For Population Genetics Analysis) software in order to determine the allelic frequencies of all the animals. When all animals in the three zones were treated as one population, allelic frequencies were 0.80 for allele A and 0.20 for allele. Also a 27.9% of heterocigosity was observed and lack of Hardy – Weinberg equilibrium was noticed (P< 0.05). In each zone, results indicated that all populations were in Hardy-Weimberg equilibrium (P>0.05).
