Breast milk provides an excellent supply of most nutrients for newborn infants. Infant formulae should be nutritionally comparable to breast milk especially with regard to critical nutrients like iron and other trace elements. Infant formulae supplemented with various amounts of bovine lactoferrin were given to two groups of infants. These infants were compared with infants receiving unsupplemented formula and breast-fed infants. The effects of these diets on levels of haemoglobin, haematocrit, serum iron, ferritin and zinc were examined for a study period of 150 days. At birth, concentrations of iron, haemoglobin, haematocrit and zinc were comparable in all four feeding groups. The fact that the serum zinc level was not altered by lactoferrin supplementation appears to rule out an in-vivo effect of lactoferrin on zinc nutrition of infants. Ferritin levels of breast-fed infants were significantly higher than in non-supplemented formula-fed infants at day 30 and day 90. This difference was seen only at day 30, when comparing breast-fed infants to lactoferrin-supplemented formula-fed infants. Comparing the infants receiving formulae, the formula supplemented with the higher amount of bovine lactoferrin induced significantly higher serum ferritin levels compared to the unsupplemented formula at day 90 and day 150. These observations favour the idea that lactoferrin may be involved in iron absorption. Since this effect was pronounced only after 90 days, it has to be discussed as to whether this effect is a convincing argument for supplementing infant formulae with bovine lactoferrin.