A study was made of weight gains and carcass compositions in response to dietary sucrose, glucose, fructose, and corn starch at two dietary levels (40 and 60 %). Protein in the diets was either minimally adequate (12 %) or in excess of the requirement (18 %). At both carbohydrate and protein levels, sucrose-fed rats showed significantly greater weight gains than those animals receiving the other carbohydrates. At the 40-percent level, corn starch-fed animals gained more weight than animals receiving either glucose or fructose. At the 60-percent level, animals presented with fructose gained less weight than animals receiving the other carbohydrates. The animals receiving sucrose at both dietary levels had more carcass fat than those receiving either glucose or corn starch, and more carcass fat than those receiving fructose at the 60-percent level. An inverse relationship existed between carcass fat and carcass protein when both were expressed as a percentage of carcass dry weight. The fructose diets had protein retention values intermediate to those seen on the other diets. Protein retention on the sucrose diets was at least as high or higher than that on the starch diets. The results are consistent with the concept that different dietary carbohydrates elicit differing metabolic responses as measured by both weight gains and carcass analyses.