This study was conducted to determine the carcass rates, partcarcass production percentages, nutrient contents and optimum prices of broilers and old layers as related to the body weight. Total 240 birds were used and results obtained are summarized as follows. 1.The carcass rates were 61.41% in young chickens (0.6-0.8kg), 65.07% in semi-bros(1.2-1.4kg) and 66.39% in high- bros (1.7-2.1kg), showing a trend of increased carcass rate as the body weight increased. The carcass rates of old layers were lower than those of broilers, being 62.68% in white old lavers (1.8-2.0kg) and 63.07% in colored old layers (2.1- 2.4 kg) 2. Although there was little difference in part-carcass production percentages between breeds or body weights of broilers, most of the part-carcass was produced from legs, breast, back, wings and neck in order. 3. As the body weight increased, the moisture content of deboned carcass of broilers decreased (71.27% in young chickens, 62.66% in semi-bros and 60.39% in high-bros), while the fat content increased (11.47% in young chickens, 17.60% in semi-bros and 19.87% in high-bros). The protein content of semi-bros (17.21%) was higher than that of young chickens (14.75%) or high-bros (16.93%), but no difference was noted in old layers whether they were white or colored. 4. When compared on the basis of protein or Protein plus fat content in grams per kilogram body weight, the market price of semi-bros per kilogram body weight was more expensive and that of old layers was cheaper than that of high- bros.