RSV is a major cause of lower respiratory illness (LRI) in childhood. T-helper cytokines are present in the respiratory secretions of asthmatics, but have not been studied in secretions of infants with RSV infection. We obtained nasopharyngeal secretion specimens (NPS) from healthy infants ≤15 months of age who were hospitalized for acute RSV LRI, and determined the presence of IL-4, IL-10, IFN-δ and eosinophil cationic protein (ECP). NPS were obtained on the first day of hospitalization (mean 3.2±1.0d from onset of symptoms). A previous history of wheezing episodes was sought. Respiratory evaluation included chest auscultation and Xray, respiratory rate and oxygen saturation. In first wheezing episodes, all three cytokines were frequently detectable (as was ECP), and a direct correlation of IL-10 and IFN-δ was noted (p=0.004). The presence of IL-4 was related to greater hypoxia (p=0.047). In infants with recurrent wheezing, mean concentrations of all three cytokines and of ECP were greater than during the first wheezing episodes, significantly for IFN-(p=0.02) and ECP (p=0.03). IFN-δ and IL-10 were again positively correlated (p=0.001) and IFN and IL-4 were correlated less strongly. The content of ECP was related to that of IL-10 (p=0.01). These results indicate that T-helper cells are activated during early RSV infection, and to a greater degree with recurrent wheezing. However, the T-helper type 1 and 2 profiles appear to be reasonably balanced, suggesting that other mechanisms account for eosinophil activation and disease severity.