Wean-to-finish production, which involves taking pigs from weaning to slaughter in the same building, is becoming widely adopted in the US swine industry. This production system is being advocated largely because of claims of improved animal performance and a decrease in labor needed for animal movement compared to conventional multiple-stage systems. One of the potential disadvantages of this system is the considerable underutilization of floor space during the early growth period if pigs are penned in the group sizes that are appropriate for finishing pigs. However, increasing the stocking rate initially at weaning, with some of these pigs subsequently being moved to another finishing facility, may increase output from the system. Therefore, the objective of this research was to investigate effects of initial stocking rate and of feeder-trough space in commercial wean-to-finish facilities on pig performance from weaning to slaughter.