The objects of this study were to estimate the heritabilities, phenotypic and genetic correlations among productive traits and to find optimum selection method based on genetic parameters for each trait in dairy cattle. The data used in this study were obtained from the Holstein Friesian cows of The National Livestock Breeding Station. There were 1429 records from 354 cows, representing 44 sires. The data collected from 1969 through 1981. The traits studied were Milk Yield, Fat Yield, Fat Percentage, Peak Yield and Peak Lactation Period. The results obtained in this study were summarized as follows; 1. In the average performance of productive traits, milk yield was 4820.32 ± 1152.05 ㎏, fat yield 170.29 ± 41.62 ㎏, fat percentage 3.54 ± 0.33 %, peak yield 24.31 ± 5.75 ㎏ and peak lactation period 44.12 ± 27.39 day. As compared with average foreign report, above average performances showed low trend except peak lactation period. 2. The heritability estimates from sire component were 0.211 for milk yield, 0.249 for fat yield, 0.520 for fat percentage, 0.236 for peak yield, 0.199 for peak lactation period. As a result, these traits are not high heritable characters except for fat percentage. 3. The genetic correlation coefficient of milk yield with fat yield was 0.841, milk Meld with fat percentage -0.098 and fat yield with fat percentage 0.458. Relationship of milk yield was measured to be 0.518 with peak yield, 0.744 with peak lactation period. Expected genetic change in productive traits based on a phenotypic selection differential was also studied. Therefore, direct selection may be more effective than indirect selection.