A line of Yorkshire pigs was selected for 3 generations for reduced residual feed intake (RFI), a measure of feed efficiency defined as feed consumed over and above average requirements for maintenance and growth. Heritability estimates of RFI, feed intake, growth, and backfat were 0.30, 0.46, 0.33, and 0.67. Comparison of performance of gilts from the selected line (n=49) to those of a randomly selected control line (n=38) from ~40 to ~70 kg showed that selection had significantly decreased feed intake by 123 g/d. There were no significant differences in average daily gain and backfat between the lines, although the selection line tended to have 22 g/d less growth. In conclusion, RFI is a heritable trait and selection for RFI has significantly decreased the amount of feed required for a given rate of growth and backfat.