Objective: We hypothesized that very low birth weight (VLBW) infants have reduced serum and red blood cell (RBC) selenium (Se) at birth, which decrease further with current nutrition and are associated with chronic lung disease and septicaemia. Design: We studied Se intake, concentration in serum and RBCs and glutathione peroxidase (GSH-Px) activity in preterm and term infants from birth until 16 weeks. Data are mean7standard deviation (s.d.). Setting: Seventy-two preterm infants in two groups, born in Berlin, gestational age 26 þ 0/30 þ 0 weeks, birth weight 845/ 1270 g, with low Se intake (2.270.8/2.571.2 mg/kg/day), and 55 term infants, gestational age 39 þ 1 weeks, birth weight 3160 g, born in Venezuela (high Se intake: 2978 mg/day). Results: A balance study in 10 preterm infants showed that Se is well absorbed from human milk (7779%). Serum concentration was higher in term (142.0740.0 mg/l) than in preterm infants (17.878.1/19.972.2 mg/l) at 4/7 weeks. Serum and RBC concentration of Se declined in all infants, low values in preterm infants did not correlate with chronic lung disease and septicaemia. GSH-Px activity in RBCs remained stable until 6 weeks of age in all infants and was not correlated with Se in RBCs. Conclusions: Se concentration in serum decreases during the first weeks of life and depends on intake. GSH-Px activity is not useful as a marker for Se status in infants up to 16 weeks after birth.