A total of 957 lactation records from 571 Holstein dairy cows were tested every 10 days from 1989 to 1997 at the National Livestock Research Institute. The cows were milked twice a day. A peak milk yield was found at 60 days in milk, and heritability of peak milk yield was 0.31, and the genetic correlation of cumulative milk yield of early stage of cows with 305DIM were showed to be 0.35 to 0.65. From these results, selection of cows could be made earlier by using milk records at earlier stages.