Airway inflammation is an early feature of asthma. Early detection and anti-inflammatory treatment may have important therapeutic impact. Exhaled nitric oxide is a noninvasive marker of airway inflammation. The current study investigated the association between exhaled nitric oxide and asthma, wheezing phenotypes, atopy and blood eosinophilia in a large group of 4-yr-old children from the general population. All children participated in the Prevention and Incidence of Asthma and Mite Allergy study, a birth cohort study of high-risk (atopic mother) and low-risk children in the Netherlands. Nitric oxide levels were successfully determined in 429 children. Although there was overlap in the distribution of values of children with and without asthma or atopy, mean values were higher in children with atopy or doctor's diagnosed asthma (geometric mean (ppb) 9.4 and 10.0, respectively) as compared to those without (7.7 and 7.9). Values were highest in atopic symptomatic children. Values were not associated with wheezing phenotype or blood eosinophilia. This study is one of the few large-scale epidemiological studies among 4-yr-old children from the general population showing that children with symptoms of asthma and atopy have higher levels of exhaled nitric oxide than those without.