A study was conducted to determine the effect of breed, sex and diet on the carcass composition of chickens. Male and female chicks of the Light Brahma, White Plymouth Rock, Single Comb White Leghorn, Black Jersey Giant and Dark Cornish breeds were fed three diets of widely varying calorie:protein ratios to four weeks of age. The Black Jersey Giant chickens attained the greatest weight at 4 weeks followed by the White Plymouth Rock, Dark Cornish and Single Comb White Leghorn with the Light Brahma growing the slowest of the strains tested. Significant differences in the quantity of moisture, protein, total lipid and ash present in the total carcass was found among certain breeds. The Light Brahma contained the largest amounts of total lipid, 10.4%, followed by the White Plymouth Rock, 10.2%, Black Jersey Giant, 9.5%, Single Comb White Leghorn, 8.8%, and the Dark Cornish, 8.6%. Both sex and diet also caused differences in the total body composition. Significant differences in the amounts of certain fatty acids in the carcasses of the various breeds were found; however, these differences were not great.