One hundred and thirty-five infants of atopic parents were exclusively breast-fed for 6 months without any cow's milk based supplements. Of these infants 70 received no nourishment except breast milk during the 6 months, and 65 were started on solid foods at the age of 3 months. The diet of all the infants was similar during 6 to 12 months of age. The children were examined at the age of one year. In the exclusive breast milk group atopic eczema and food allergy were less frequent than in the solid food group. The results suggest that total solid food elimination for the first 6 months of life, in addition to exclusive breast milk feeding, is prophylactic for atopic disease in children who are at hereditary risk.