Previous research has indicated that selection for improved feed conversion ratio (feed:gain) in growing-finishing cattle will enhance growth rate but increase mature cow size and likely increase maintenance costs. Recent research has focused on a different measure of efficiency, residual feed intake (RFI), which is defined as the difference between an animal’s actual feed intake and its expected feed requirement. An animal with a low RFI would be more efficient than one with a high RFI and vice versa. Some recent studies have reported that low and high RFI steers do not differ in growth but low RFI steers have a leaner body composition. In this Lacombe Research Centre project, 176 crossbred steers were used to determine relationships between RFI and growth rate, body composition and heat production (HP), and to quantify differences in RFI independent of differences in body composition. Low RFI steers consumed less dry matter, had an improved feed:gain ratio, greater ribeye area, lower marbling score, and lower yield grade number than medium and high RFI steers. Low RFI steers also had lower metabolizable energy intake, retained less energy, and produced less heat than high RFI steers. Furthermore, liver, small and large intestine, and stomach and intestine weights were lower in low and medium RFI steers than in high RFI steers. There was a trend for low RFI steers to have less dissectible carcass fat, less seam fat, and a slower accretion rate of empty body fat then medium and high RFI steers. This study confirms other research that suggests RFI groups differ somewhat in body composition. This led the authors to conclude that an attempt should be made to adjust RFI for changes in the chemical composition of gain (Basarab et al. 2003. Can. J. Anim. Sci. 83:189).