It is now some 50 years since iron-binding lactoferrin was first isolated and purified, an event that opened the way to subsequent extensive research on lactoferrin structure and function. The initial recognition that lactoferrin closely resembled the plasma iron-transport protein transferrin meant that lactoferrin was first thought to mediate intestinal iron absorption or to act as an antimicrobial agent. It was also suggested that it could mediate the hyposideraemia of inflammation. This paper will assess to what extent early proposals have stood the test of time and also suggest possible mechanisms by which lactoferrin can mediate the large number of potential functions that have subsequently been proposed. It will also review the ability of lactoferrin to resist digestion in the gastrointestinal tract and identify areas for future research.