This work was carried out on twelve adult birds of each of fowl duck and pigeon. The morphological features of the pectoral muscle (Pars thoracis) were described. In addition the weight, length and thickness of this muscle were also recorded. The cross sectional area (CSA) of the muscle bundles and muscle fibers were measured. The thickness of the pectoral muscle and the percentage of its weight to that of the body weight, as well as the percentage of the length of the sternal carina and the furcula to the length of Assiut Vet. Med. J. Vol. 41 No. 82, July 1999. the pectoral muscle show the highest value in the pigeon (flying bird), followed by duck (swimming bird) then the fowl (walking bird). According to the CSA of the muscle fiber, the pectoral muscle of fowl consists almost entirely of one type of muscle fiber, while that of the duck and pigeon consists of two types, small and large. The CSA of the large muscle fiber in pigeon has generally four and half folds that of small fiber, while in duck the former fiber is two folds that of the latter one.