It has been hypothesized that decreasing antioxidant (fruit and vegetables), increased n-6 polyunsaturated fatty acid (PUFA; (margarine, vegetable oil), and decreased n-3 PUFA (oily fish) intakes have contributed to the recent increases in asthma and atopic disease. Epidemiologic studies in adults and children have reported beneficial associations between dietary antioxidants and lipids and parameters of asthma and atopic disease. The associations with n-6 and n-3 PUFA appear to be very complex and might differ between asthma and atopic dermatitis. Dietary antioxidants are probably exerting antioxidant and nonantioxidant immunomodulatory effects. Dietary lipids exert numerous complex effects on proinflammatory and immunologic pathways. It has also been suggested that atopic dermatitis is associated with an enzyme defect in lipid metabolism. In spite of this, the results of interventional supplementation studies in established disease have been disappointing, and there is now increasing interest in the possibility that dietary antioxidant and lipid intakes might be important in determining expression of disease during pregnancy and early childhood and that dietary interventions should be targeted at these groups. It also seems likely that there is individual variation in the responses of individuals to lipid, and probably antioxidant, supplementation. Further research to determine whether dietary intervention can reduce the risk of asthma and atopic disease is justified.