Transport losses represent three challenges for the US swine industry and these are: 1) pig well-being, 2) increased rules and regulations, and 3) direct financial losses to producers and packers. Therefore; improving the well-being of pigs during transport and reducing the incidence of dead and non-ambulatory pigs is a priority for the US swine industry (NPB, 2007). Johnson et al. (2010) studied the effects of grow-finish pen size and manually pre-sorting pigs the day before loading on the stress responses at loading and unloading and transport losses in market weight pigs. The authors reported that pigs loaded from large pens (192 pigs/pen) that were pre-sorted from pen mates had 66% fewer dead and non-ambulatory pigs at the harvest facility compared to pigs loaded from small pens (32 pigs/pen) that were sorted from pen mates during loading. However, it is unclear if the reduction in transport losses was due to pen size and/or pre-sorting before marketing. Therefore, the objectives of the current two research trials were to 1) determine the effects of pre-sorting prior to loading on stress responses and transport losses at the harvest facility in the market weight pig; and 2) determine the effects of grow-finish pen size on stress responses and transport losses at the harvest facility in the market weight pig.