In this study, the hind legs' muscle, one of the important parts of chicken body for meat production, was compared quantitatively with its weight among various breeds and sexes. Males and females of Rhode Island Red (RIR), Barred Plymouth Rock (BPR), White Leghorn (WL) and males of White Cornish (WC) were used from 2 to 18-19 weeks of age. Weighing of skeletal muscle was done in the hind legs' part and its three different subparts (pelvis, femur, crus). Regression equations of males and females of each breed were calculated between the muscle weight of these parts and live weight or total muscle weight. And the equations were applied to the study of ability of meat production. The results were as follows: Specific individual ability of meat production in the hind legs' part and its three subparts was observed among all breeds and sexes. This individual ability was controlled by two factors; one was the rate of increase of the live weight, and the other was the rate of increase of the individual muscle percentage weight against the live weight. In males, RIR showed the highest value of muscle percentage weight of all breeds, and high ability of meat production in the hind legs' part. When the muscle percentage weight was compared between WC and RIR at the same live weight, WC showed always lower value than RIR. But WC was the better meat producer than RIR in the hind legs' part, because of its rapid rate of increase of live weight. BPR showed the highest value of muscle percentage weight until 1 kg of live weight. WL exhibited the worst ability of meat production of the hind legs' part, because of both factors, namely low value of muscle percentage weight and slow rate of increase of live weight. In females, the muscle percentage weight did not show any differences between RIR, BPR and WL in the hind legs' part, and also between sexes. The percentage weight of hind legs' muscle to total muscle weight did not change in WC males, but it increased in other breed males and females. These results suggest that the ability of meat production of hind legs' part is better than that of other parts in the body. When hind legs' part was divided into three subparts, the ability of meat production of each subpart was also discussed. The percentage weight of crural muscle to live weight increased conspicuously in RIR. The percentage weights of crural and pelvic muscles to total muscle weight in RIR showed the largest value also. The percentage weight of femoral muscle to total muscle weight was largest in BPR.