This study was conducted to improve the interior egg quality with a total of 6,093 eggs, laid at 351 Single Comb White Leghorns and 326 Rhode Island Reds, produced at National Livestock Breeding Station from March 1, 1979 through July 30, 1980. The results obtained are summarized as follows; 1. The average albumen height of the eggs at first eggs, 300 and 500 days of age was 8.32, 7.51 and 6.74㎜ in the S.C.W. Leghorn and 8.04, 6.94 and 6.05㎜ in the R.L.Red, and the Haugh units at first egg, 300 and S00 days of age was 90.92, 79.74 and 76.25 in the S.C.W. Leghorn, and 88.54, 80.02 and 74.56 in the R.I. Red, also the egg shell thickness at first egg, 300 and 500 days of age was 0.383, (1.364 and 0.334㎜ in the S.C.W. Leghorn and 0.354, 0.332 and 0.327 in the R.I. Red. 2. The heritability estimates in the S.C.W. Leghorn and R.I. Red were 0.398∼0.847 and 0.306∼0.634 for albumen height, 0.162∼0.594 and 0.125∼0.485 for Haugh units, 0.185-0.339 and 0.176∼0.402 for egg shell thickness, respectively. 3. The genetic correlation coefficients between the interior egg qualities were as follows. In the S.C.W. Leghorn and R.I. Red, the coefficients between albumen height and Haugh units, 0.432∼0.845 arid 0.397∼0.974; between albumen height and egg shell thickness, 0.046∼0.226 and 0.068∼0.197; between Haugh units and egg shell thickness, 0.089∼0.364 and 0.165∼0.327 ; respectively.