The purpose of this study was to determine whether selenate fortification of infant formula would improve the selenium status of relatively well, growing, preterm infants during the first 12 wk of enteral feeding. A high-selenium group (n = 7, mean body weight = 1312 g) received selenate-fortified preterm and full-term infant formulas containing 0.36 and 0.22 mumol Se/L, respectively, and a low-selenium group (n = 10, mean body weight = 1262 g) received non-selenium-fortified preterm and full-term infant formulas containing 0.12 and 0.11 mumol Se/L, respectively. There were no significant differences in growth between the two groups throughout the study. The high-selenium group had significantly greater mean selenium intakes than did the low-selenium group from weeks 2 to 12. Plasma selenium concentrations decreased over the study period in the low-selenium group. Plasma selenium-dependent glutathione peroxidase activity was greater in the high-selenium group at week 12 only. Red blood cell selenium concentrations decreased over time in both groups and were significantly greater in the high-selenium group at weeks 4, 8, and 12. Plasma selenium concentrations were significantly correlated with plasma glutathione peroxidase activity for all infants on study day 1 and at weeks 4 and 12. Selenium intake of all infants was significantly correlated with plasma glutathione peroxidase activity at 12 wk. Selenate fortification of infant formulas can improve the selenium status of preterm infants. Current selenium contents of infant formulas and recommendations for dietary intakes of selenium for some preterm infants may be inadequate.