Abstract: Milk protein polymorphism such as β-Lg of Holstein dairy cows were investigated in this study. The relationships between milk protein genotypes and some milk production traits were determined. Genetic variants of milk protein were identified by horizontal starch-gel electrophoresis containing mercaptoethanol and urea. The allelice frequencies of A and B were found to be 0.362 and 0.648, respectively. Genotype frequencies were in accordance with the Hardy-Weinberg equilibrium. Milk production traits chosen in relation to β-Lg variants were: actual milk yield, 305 days milk yield, actual fat yield, 305 days fat yield, fat percentage in milk, lactation length. The effect of β-Lg genotypes on milk production traits were analysed using a General Linear Model (GLM). There was no significant association between different genotypes of β-Lg and milk production traits of the analysed cows.