Summary Thirty gravid mares of different breeds and in steady-state selenium (Se) nutrition were used to demonstrate a significant positive correlation between blood Se concentration and glutathione peroxidase (GSH-Px) activity. The relationship between blood Se and GSH-Px activity was higher in mares than in foals at parturition. The Se status of foals was also significantly correlated with that of the respective mares at parturition under practical management conditions where wide variations in dietary Se during gestation were present. Selenium concentration of milk was less than one-fourth of that in colostrum within one day postpartum and was considered a minor source of Se for the foals regardless of Se status of the mares during gestation. There were no significant differences in blood Se concentration between mares and foals of low Se status at parturition or during a 4-week postpartum interval. For mare/foal pairs of adequate Se status, however, the differences were significant throughout the experimental period. Foals in this group had higher blood Se concentration than either foals or mares of low Se status. Plasma vitamin E concentration was elevated 3–4 fold in all foals by 1 day postpartum, following colostrum ingestion, and was independent of the Se status of their dams. We did not observe clinical signs of white muscle disease during a 4-week postpartum period or differences in serum enzymes indicative of muscle damage in any of the foals regardless of their Se status.