The authors have studied the evolution of serum transferrin concentration in relation with age (newborn child, infant, adult). The mean concentration of serum transferrin is the lowest for neonates (2.15 g/l). At 10 months, it increases to reach a value of about 3.10 g/l then reduces at 24 (3.0 g/l) and 48 months (2.8 g/l). By the 4 to 18 years subjects, serum transferrin is approaching that of 10 months children (3.15 g/l). At last it doesn't support any modification during all the adult life. The diversity of the obtained results dependent of the used technique and/or of the laboratory, justifies that each one defines his own reference values.