Milk protein polymorphism such as beta-Lactoglobulin (beta-Lg) of Brown-Swiss 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 allelic frequencies of A and B were found to be 0.375 and 0.625 respectively. Milk production traits chosen in relation to beta-Lg variants were: actual milk yield, 305 d milk yield, actual fat yield, 305 d fat yield, fat percentage in milk, lactation length. Genotype frequencies were in accordance with the Hardy-Weinberg equilibrium. The effect of beta-Lg genotypes on milk production traits were analyzed using a general linear model (GLM). There was no significant association between different genotypes of beta-Lg and milk production traits of the analyzed cows.