On an average the newborn infant serum compared to the normal adult male is hyperferremic (S.I. 193 µg./100 cc.), hypocupremic (S.C.51µg./100 cc.), and his free erythrocyte protoporphyrin is increased about two-fold (E.P. 55 µg./100 cc.). His total serum iron-binding capacity appears to be 50% or more saturated. At 12 hours of age marked hypoferremia (S.I. 46 µg./100 cc.) is present and the total iron-binding capacity as measured in this study is 100% saturated. There is slight, if any, change in the serum copper or erythrocyte protoporphyrin during the first few hours or days of life. From two weeks through one month of age an essentially normal pattern is present except for the slightly elevated (two-fold) protoporphyrin. By 4 to 10 months of age, on an average, the normal infant has the pattern characteristic of infancy, namely, hypoferremia (S.I., 50 µ. g/100 cc.), hypercupremia (S.C., 146 µg./100 cc.), reduced saturation of the total serum iron-binding capacity (12%) and elevated free erythrocyte protoporphyrin (E.P., 70 µg./100 cc.). Extreme ranges in values are found in different individuals at most ages. The suggested explanation for these findings is that on an average, the normal infant relative to the adult is totally depleted of his iron reserve and that his state of "physiologic anemia" constitutes an additional, but lesser, iron deficit.