A variety of "hypoallergenic" formulas have appeared on the market over the last few years for feeding lactating infants prone to a high atopic risk of allergy to cow's milk. These formulas consist of soya preparations, hydrolyzed proteins and so-called basic formulas. This paper describes the main characteristics of such formulas, with particular emphasis on their tolerance, indications, related immunological aspects and antigenic capabilities. Notifications of anaphylactoid reactions with hydrolyzed proteins and the possibility of interactions with the IgE antibodies in cow's milk indicate such formulas in cases of non-IgE-mediated intolerance. Although soya preparations may be allergenic, they do not present interactions with the proteins in cow's milk; thus, they are particularly indicated in children with protein allergy to cow's milk with specific IgE antibodies.