The objectives of this study were to evaluate the dialysed quantities of amino acids and minerals (calcium, phosphorus, magnesium, iron and zinc) in two types of infant formulas, one with a basis of native cow milk proteins and the other highly hydrolysed, to evaluate the possible application of Miller's in vitro method in amino acid and mineral availability studies. The percentage of dialysis differed between proteins. The hydrolysis treatment applied to the proteins significantly increased the dialysis percentage of almost all the amino acids. The dialysability of all the minerals was statistically greater in the formula made with a basis of hydrolysed proteins. Miller's method was seen to be of use for showing the effect which the hydrolysis treatment has on the availability of amino acids. Despite its limitations of having to be carried out in vitro, the study suggests that the nutritional value in relation with amino acids, minerals and trace elements differs between the both types of formulas.