Cow's milk is a major food for young children. Whole cow's milk is known to be detrimental to infants, mainly due to its low iron content. The negative association with iron status led to recommending the introduction of formula feeding in infancy during the weaning period or when breastfeeding ceased. More recently, the literature suggests that consuming whole cow's milk in infancy has unfortunate effects on growth, especially weight acceleration and development of overweight in childhood. These issues are discussed in the following chapter. Other suggested reasons for the avoidance of whole cow's milk in infancy are touched upon, such as milk protein allergy and high renal solute load. The hypothesis about early cow's milk introduction in the pathology of certain diseases, mainly through the peptide β-casomorphin-7, is briefly reviewed, showing that there is no clear evidence for the suggested associations. The chapter gives a recent example of introducing formula at 6 months of age instead of whole cow's milk in infants' diet in Iceland. Several aspects of consuming whole cow's milk in infancy can be found in recent reviews.