Abstract: A Polymerase Chain Reaction-Restriction Fragment Length Polymorphism (PCR-RFLP) test was performed on DNA samples extracted from blood samples of Brown Swiss cattle to detect genotype frequency of the bovine kappa-casein (CNS3) locus. A 351 bp fragment of CSN3 was amplified and digested with Hinf I restriction enzymes. Samples were loaded on agarose jel (3%) and genotyped under UV light. Three genotypes were observed, frequencies were 19.35, 20.43 and 60.22% for AA, BB and AB, respectively. Two genetic variants CSN3 A and CNS3 B were identified and the allelic frequencies were estimated as 0.495 and 0.505, respectively. It was concluded that the population was in Hardy-Weinberg equilibrum.