This experiment was carried out to investigate appropriatencess in application of NRC (1977) protein requirement for broiler chick in Korea. Growth rate, feed efficiency, nutrient utilizability and feed cost affected by dietary protein levels(23-21%, 11-19%, 19-17% and 17-15% respectively in starting and finishing period) and sexes were examined. Results obtained from the present study can be summarized as follows: 1. It was found that growth rate was significantly improved (P$lt;0.01) as the dietary protein level was increased. Significant differences in growth rates of both male and female were found among all the different protein levels (P$lt;0.05). 2. Significantly less feed (P $lt;0.05) has been consumed by the chicks fed low level of dietary. protein in both male and female. Male consumed slightly more feed than female did, and significance was found at only 19-17% dietary protein level (P$lt;0.05). 3. No statistical difference (P$lt;0.05) was found among protein levels or between both sexes except female at 23-21% dietary protein level. But feed efficiency was improved Tightly as the level of dietary protein increased. 4. Utilizability of dry matter, crude protein, ether extract and NFE in the rations have been slightly improved with increment of dietary protein level. Increasing the dietary protein level resulted in improved nitrogen retention. 5. Feed cost per ㎏ body weight gain of chicks was the cheapest when the dietary level of protein was the lowest, and that of male was cheaper than that of female.