Cow milk allergy can be defined as an adverse immunologic reactions to cow milk protein. The term is often mistakenly applied to other causes of milk intolerence, such as lactase deficiency and galactosemia, which must be differenciated and excluded. We have experienced 10 children of cow milk allergy at neonatal onset who had suffered from G-I symtoms, such as diarrhea, irritability, weight loss, vomiting and abdominal distension. One half of this patients had family history of allergic diseas. All patients have positive specific IgE RAST to cow's milk protein, milk elimination test and milk challenge test. Brest milk feeding and soy bean formula feeding and soy bean formula feeding have started after diagnosis and then gastrointestinal symtoms and signs of all patients are improved but other allergic diseases are combined in 5 children.