Objectives: Infants with cow's milk allergy (CMA) are in need of a substitute formula up to 2 years. The are three requisites for a substitute of milk in CMA: tolerability, nutritional adequacy, and cost-effectiveness. We evaluate here the tolerability of a new amino acid-based infant formula for the management of CMA. Methods: In a phase III/IV prospective, multicentre, open-label, international study, infants and children with immunoglobulin E-mediated CMA were exposed to a diagnostic double-blinded, placebo-controlled food challenge with a new amino acid formula by Blemil Plus Elemental using Neocate as the placebo. If tolerant to it, the study formula was integrated into the patients' usual daily diet for 7 days. Efficacy on day 7 was assessed in terms of symptoms associated with CMA, amount of formula consumed, nutritional and energy intake, and anthropometric data. Results: Thirty children (17 M and 13 F; median age, 1.58; range, 0.08-12.83 years) completed the open challenge and were able to consume the study formula for at least 7 days. No signs or symptoms of allergic reactions were recorded among children assuming either the test or the control formula, with a lower 95% one-sided confidence interval for the proportion of subjects who did not experience allergic reactions above 90%. Sixteen patient under the age of two continued with the optional extension phase. Conclusions: The study formula meets the American Academy of Pediatric criteria for hypoallergenicity and is well tolerated in short-term use. During optional phase, growth of the patients was not hindered by the study formula.