Crossbreeding in commercial hog operations is widely practiced and has increased substantially in recent years. Perhaps the most important positive feature of crossbreeding is heterosis, i.e., the performance of crossbred progeny is superior to the average performance of the parents. In addition, producers have much wider options in breeding for desired carcass traits and sire and dam characteristics when blending breeds than when making genetic selection within any single breed. The costs to the firm are primarily managerial because of the necessity of buying replacements, frequently rotating boar breed, or maintaining miniherds to produce replacements for the breeding herd. Over the long run there is also a potential cost to the industry of reducing the number of purebred lines from which the crossbreds are derived and thus slowing genetic improvements within breeds.