Outdoor reared pigs are said to suffer from less of a growth check post weaning than their indoor reared counterparts (Payne et al. 2003) and have more developed gut post-weaning (Carroll et al. 2007). Zinc oxide (ZnO) is often used in weaner diets to reduce the incidence of post weaning scours. Previous work by Miller (personal communication) conducted at the University of Leeds identified differences in circulating serum IgG concentrations associated with rearing environment and antimicrobial supplementation post-weaning. Conducted as part of a larger experiment, the aim of this preliminary study was to investigate the effects of ZnO medication of weaner diets upon immune status immediately post-weaning in both indoor and outdoor reared pigs. We hypothesised that piglets reared outside would exhibit a less activated immune response than indoor reared pigs post-weaning and that the presence of ZnO would further reduce immune activation.