SUMMARY:The physical properties of the major muscles of the round from 30 crossbred beef and 20 straightbred dairy carcasses were studied. Sex, sire and body type were related to these properties. Generally, the steers had longer, heavier and lighter‐colored muscles than the heifers. A negative relationship was noted between the specific gravity and reflectance values for the crossbred muscles. The semimembranosus muscle was heaviest and accounted for the highest percent of the rough round in certain beef and dairy sire groups. In the dairy cattle, the weight of the biceps femoris muscle was also affected by sire. Heritability estimates indicated that the weight of the semimembranosus was highly heritable and its percent of the rough round moderately heritable in both beef and dairy cattle. The dairy b. femoris weight and circumference were also moderately heritable. Color reflectance, specific gravity, pH, length and circumference/length ratio were not observed to be heritable physical propertie
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