As an antioxidant, selenium stimulates Th1 immune response against viral infections, and may play a role in the pathogenesis of frequent wheeze due to respiratory viral infections during the first year of life. We investigated the level of selenium in children with frequent wheeze who had no atopic diseases and no family history of atopy to determine whether selenium has an effect on the severity of the diseases. Sixty-one children with frequent wheeze who were in the asymptomatic period and had had no infectious disease for two months and an equal number of age- and sex-matched children, as a control group, without atopy or allergy or systemic diseases were enrolled in the study. In the study group, we determined the levels of serum selenium, total IgE, mixed specific IgE, and total eosinophil count, and we performed epidermal prick tests. Serum selenium levels were (mean and SEM) 61.95 +/- 1.23 microg/L in the study group and 72.71 +/- 1.28 microg/L in the control group (p < 0.001), and there was a negative correlation between the serum selenium levels and number of wheeze attacks during the previous year (r = -0.655; p < 0.001). As a result, selenium may play a role in the progression of respiratory infections during childhood and can be accepted as a risk factor for development of wheezing.