We examined the relationship of diet to the development of atopic manifestations in a group of infants with an immediate family history of atopy, followed prospectively from birth for up to 20 months of age. There was no relationship between the development of atopic dermatitis, rhinitis and wheeze and either 2 or 4 months exclusive breast feeding, or the introduction of cow's milk or solids in the first 4 months of life. In addition there was no relationship between the introduction of milk, egg or wheat into the diet and the development of skin-test positivity to these foods. In fact, five infants developed positive skin tests to the food prior to its introduction into the diet, suggesting exposure via maternal breast milk. Thus we have been unable to show a protective effect of either breast feeding or cow's milk or solid avoidance on the development of atopic disease in infancy.