The aim of the study was to estimate the effect of the butyrophilin (BTN) and growth hormone receptor (GHR) gene polymorphisms on the breeding value of genotyped AI bulls for milk production traits. A total of 131 Holstein-Friesian bulls were analysed. The following allele frequencies have been found: 0.88 (L) and 0.12 (A) at the BTN locus, and 0.85 (S) and 0.15 (G) at the GHR locus. The effect of genotype on milk yield and composition was tested in the group of 101 AI proven bulls. Because the number of A/A and G/G animals was very low, the gene-trait association analysis was reduced to the comparison of two remaining genotypes at each locus. No signifcant association has been found. However, bulls with the L/L genotype at the BTN gene were characterized by a higher breeding value for milk fat content than animals with the L/A genotype (P≤0.1).