OBJECTIVE: Increasing childhood asthma rates may be due to changing dietary lifestyle. We investigated the association of dietary intake of antioxidant vitamins and fatty acids with asthma in Japanese pre-school children. DESIGN: Cross-sectional study. SETTING: School-based survey on lifestyle/diet and health status in children in Japan. SUBJECTS: Parents of 452 children aged 3-6 years completed a questionnaire on the children's and parents' lifestyle and demographics. Children were classified into asthma cases and non-asthma cases in accordance with the ATS-DLD (American Thoracic Society and Division of Lung Diseases of the National Heart, Lung, and Blood Institute) questionnaire. Children's diet was assessed using a 3 d dietary record completed by parents. Children's age, sex, BMI, history of food allergy, maternal age, parental history of allergy, maternal education, family size and second-hand smoking were included as covariates. Logistic regression models were used to examine the association between children's diet and asthma. RESULTS: Compared with children with the lowest intake tertile for vitamin C and vitamin E, those in the highest were significantly inversely associated with asthma; adjusted OR (95 % CI) were 0·35 (0·14, 0·88) and 0·32 (0·12, 0·85), respectively. A statistically significant trend was also observed. Fruit intake showed an inverse but insignificant association with asthma. There were no associations of any type of fatty acids with asthma. CONCLUSIONS: These data suggest that children with high intakes of vitamins C and E may be associated with a reduced prevalence of asthma.