A national program for the prevention of atopy in children has been in progress in Finland since 1979. Its aim is to prevent or at least to reduce atopic symptoms in childhood. Since the start of the program we have followed a group of 119 children with and without a family history of atopy. Half the atopy-prone children kept to the diet intended to prevent atopy, i.e., breast-feeding prolonged up to age 3 months and introduction of solid food and formulae based on cow's milk after age 3 months. All children were examined at ages 5 and 10 years. In addition to clinical examination and interview, skin-prick tests using eight common inhalant allergens were performed. At age 9 to 10 years, 38 of the 119 children (32%) exhibited at least one atopic illness (bronchial asthma, allergic rhinitis, allergic conjunctivitis, atopic eczema or food allergy). Forty percent of children with family histories of atopy had atopic illness, independent of diet in infancy. The occurrence of atopic manifestations in the children of nonatopic families was 21%. Only half the children who had atopic symptoms at age 12 months had symptoms 9 years later. Asthma, allergic rhinitis, and positive skin-prick test results at age 5 years, however, correlated well with the subsequent occurrence of respiratory allergy. Our observations indicate that the preventive measures in early infancy intended to reduce the risk of atopy had no influence on atopic manifestations 9 years later.