Because of specific laboratory tests are lacking, diagnosis of cow's milk allergy is always made on the basis of improvement after cow's milk protein withdrawal from diet and relapsed after challenge test. However personal and familial anamnesis, supported by few simple laboratory tests (peripheral blood and stool eosinophiles, hemoccult), are important tools for diagnosis. In this work we report the clinical findings of 68 children, suffered from cow's milk allergy, observed in the last 10 years. Children were divided into three groups on the basis of challenge response: Group 1 consisting of children with averse reaction occurred within the first hour after the administration of cow's milk protein (IgE-mediated reaction, 1st class as Gell-Coombs classification); Group 2 consisting of children with averse reaction occurred between 2nd and 12th hour (1st-3rd class as Gell-Coombs classification); Group 3 consisting of children with averse reaction occurred after 24 hours the administration of cow's milk proteins (4th class as Gell-Coombs classification). Auxological parameters show that while weight is widely involved, particularly in children of group 3, height is interested only in children with prolonged diarrhoea. Cow's milk protein withdrawal from diet determine a rapid normalization of weight increment rate, more evident in children over 25th centile. Height rise up normal values slowly without any differences between children below and over 25th centile. At the age of two years 57 children (83%) became tolerant to cow's milk proteins and after 5-year follow-up in 3 children (4.4%) only persisted cow's milk allergy. All these children presented the IgE-mediate clinical form.