Dust concentrations and total and respirable endotoxin were measured in 2 types of pig-rearing facilities: an isolated nursery and nursery within a conventional farm. Dust and endotoxin concentrations were significantly higher in the conventional nursery compared with the isolated nursery. Pigs in the isolated nursery had significantly higher body weights and larger thymus glands, spleens and cervical lymph nodes than animals reared in the conventional farm. It is suggested that there may be an association between environmental facility contaminants and growth rate.