The relationship between breast or bottle feeding and the incidence of bronchitis and pneumonia in the first year of life was examined in a birth cohort of nearly 2000 children born in Harrow, England, in 1963--65. Fewer episodes of acute bronchitis and pneumonia were reported in children who were breast-fed than in children who were bottle-fed. Firstborn children were more likely to be breast-fed than subsequent children. Mothers who smoked were less likely to breast-feed their babies. Although birth order and parental smoking have been shown to be associated with bronchitis and pneumonia in the same cohort, the association between feeding pattern and respiratory illness history persisted when these and other important factors were taken into account.