Inflammation can be demonstrated in the airway mucosa of asthmatics, even in the absence of overt symptoms, but the pathogenesis of this chronic inflammation is incompletely defined. It has been suggested that inflammatory cytokines produced by epithelium may play important roles in this process. Therefore, we measured the cytokines interleukin-8 (IL-8), IL-6, and granulocyte-macrophage colony-stimulating factor (GM-CSF) in nasal lavage fluids from school-age children who were (1) "normal" (nonallergic/nonasthmatic), (2) allergic to house-dust mite antigen but nonasthmatic (no history of wheezing), or (3) allergic and asthmatic (history of > or = 10 wheezing episodes). Children underwent a single nasal lavage procedure while asymptomatic and on no anti-inflammatory medications or anti-histamines. In addition to cytokine concentrations, cell counts, differentials, albumin, histamine, and eosinophil cationic protein (ECP) concentrations were determined in nasal lavage fluids. Significant increases in IL-8 and ECP were observed in asthmatics compared with both normals and allergic nonasthmatics. Overall, IL-8 in nasal lavage fluids correlated significantly with ECP. Allergic nonasthmatics did not have significant increases in cytokines or other mediators compared with normal subjects. Concentrations of IL-6 did not differ significantly among the three groups, and GM-CSF was undetectable in all samples tested. We conclude that increased IL-8 production and eosinophil activation are characteristic of the airways of asthmatic children when asymptomatic, and we speculate that IL-8 plays a role in the maintenance of airway inflammation in asthma.