Background: Both extensively hydrolysed formulas (eHF) and amino acid-based formula (AAFs) have been demonstrated effective for the treatment of CMA. However, in clinical practice, parents complain that hydrolysates are rejected by children due to their bad taste. Flavor of hydrolysed formulas has been poorly investigated although it affects the acceptance of milk over all the other attributes. The aim of the present study was to understand the factors underlying the unpleasant flavor of hydrolysed 25 formulas and amino acid-based formula. Subjects and methods: One hundred and fifty trained panelists performed a randomized-double-blind test with different milks. The smell, texture, taste and aftertaste of each formula were evaluated on a scale ranging from -2 (worst) to 2 (best). Results: Formulas showed significant difference, as compared to cow's milk, in smell, texture, taste and aftertaste. Overall, whey eHFs were judged of better palatability than casein eHF and the AAFs (p∈