This study utilized the data from 17 randomly selected young bulls which were produced for progeny testing of dairy bulls in Korea. Semen from 17 young bulls was collected and analyzed by the PCR procedure. In order to identify the genotypic effects of milk proteins on production traits, daughter records from these bulls were also used, and the results obtained from this study were as follows 1. Semen typings of 17 domestic young bulls for detemunations of κ-casein, β-lactoglobulin, and growth hormone were undertaken. 2. After PCR amplification with restriction enzymes, 11 AA and 6 AB genotypes for κ-casein, 9 AB and 8 BB genotypes for β-lactoglobulin, as well as 12 II and s ID genotypes for growth hormone were observed among the 17 young bulls. 3. Genetic differences among genotypes(κ-CN, β-LG, bGH) for the production traits studied were significant. 4. When production yields of daughter cows were grouped by genotypes for κ-casein, all the traits except for milk-fat percent showed remarkable differences. 5. In case of indirect estimation of ganetic effects for milk protein loci, this method was very effective for the study of distributional properties in the overall dairy population.