The aim of the present work was to evaluate derivated reactive oxygen metabolites (d-ROMs) and biological antioxidant potential (BAP) in mares and foals to study perinatal oxidative status. A total of 60 animals were included in the present study. Maternal and foal venous blood samples were collected immediately after delivery along with a sample drawn from one of the umbilical arteries, and plasma samples were evaluated for lactatemia, d-ROMs, and BAP. The t test for unpaired data was applied between mares versus umbilical artery blood versus foals, both for d-ROMs and BAP. The Pearson test with two-tailed P value and a confidence interval of 95% was performed between d-ROMs and BAP and between d-ROMs and lactatemia, both for mares and foals. Finally, the t test for unpaired data was performed between fillies and colts. The t test showed differences between mares versus their own foals versus umbilical artery blood but not foals versus. umbilical artery blood, both for d-ROMs and BAP. A positive correlation was found both in mares and foals between BAP and d-ROMs and in mares between lactatemia and d-ROM. No differences in gender were found in BAP concentration. Our data are in line to previous studies performed in women and cattle.