Results of this study demonstrate that significant progress toward the enhancement of carcass composition has been realized within the Duroc breed since the mid 1980’s; however, this improvement has been at the expense of meat quality traits such as intramuscular fat. This report also suggests that the deposition rates and growth patters of loin muscle area, tenth-rib backfat, and intramuscular fat percentage have not been significantly affected by long-term selection for increased carcass leanness.