A study on the balance of essential amino acids in Korean diet and further investigation on quality of protein through optimum combination of foods using the least square method based on FAO/WHO (1973) provisional score patterns were carried out The results of the optimum gross combination are summarized as follows: 1) The first limiting amino acids of the Korean diet was found to be methionine and cysteine based on both whole egg and FAO/WHO (1973) provisional score patterns. 2) Weight ratios between rice and beef, chicken, pork, rabbit meat are 7 : 3, 4 : 1, 4 : 1, and 3 : 1. The amino acid score and the least amino acid are 100(phe+tyr), 99(thr), 111(trp), and 109(leu) for each combination. This result indicates that pork and rabbit meat can be high quality protein sources for the rice eating people. 3) Weight ratios between rice and anchovy, saury, ark shell, pollack, cuttle fish, tuna and herring are 2 : 1, 5 : 1, 3 : 2, 3 : 1, 3 : 1, 4 : 1, and 3 : 1. 4) Weight ratios between potato and rice, wheat flour are 8 : 1 and 24 : 1. Lysine, the limiting amino acid of rice and wheat flour can be complemented by combining these with potato. 5) It is possible to apply this idea on typical Korean dishes. For example, in case of soybean-sprout rice the optimum combinations of rice : soybean-sprout : pork and rice : soybean-sprout : beef are 4 : 1 : 1 and 11 : 1 : 5. It is of utmost importance to pursue further more desirable combinations with more complex food items and transform the result obtained by the computer analysis into more practical terms for practical use.