BACKGROUND: The literature regarding the association between breast-feeding and atopic diseases has been contradictory. OBJECTIVE: We have assessed the relationship between breast-feeding and atopic disorders in a cohort followed into middle age. METHODS: The Tasmanian Asthma Study is a population-based prospective cohort study that has followed participants from the age of 7 to 44 years. Exclusive breast-feeding in the first 3 months of life was examined as a risk factor for atopic diseases by using multiple logistic regression and generalized estimating equation analyses. RESULTS: At age 7 years, exclusively breast-fed children with a maternal history of atopy had a marginally lesser risk of current asthma than those not exclusively breast-fed (odds ratio [OR], 0.8; 95% CI, 0.6-1.0). However, after age 7 years, the risk reversed, and exclusively breast-fed children had an increased risk of current asthma at 14 (OR, 1.46; 95% CI, 1.02-2.07), 32 (OR, 1.84; 95% CI, 1.06-3.3), and 44 (OR, 1.57; 95% CI, 1.15-2.14) years. Exclusively breast-fed children also had a reduced risk of food allergy at age 7 years but an increased risk of food allergy (OR, 1.26; 95% CI, 1.1-1.5) and allergic rhinitis (OR, 1.2; 95% CI, 1.0-1.3) at 44 years. CONCLUSION: Exclusively breast-fed babies with a maternal history of atopy were less likely to develop asthma before the age of 7 years, but more likely to develop asthma after the age of 7 years. CLINICAL IMPLICATIONS: The current recommendation to breast-feed high-risk infants for protection against early wheezing illness can be confirmed. However, the recommendation should be reconsidered for protection against allergic asthma and atopy in the longer term.