In mild asthmatics, the study will investigate: (1) if exposure to ozone will enhance the viral infective process in the nasal epithelium, (2) the effect of ozone exposure on RV-induced inflammatory gene expression, mediator release and inflammatory cell influx into the upper and lower airways, and (3) the interactive effects of ozone and RV on airway reactivity. This information will improve our understanding of the risk associated with oxidant pollutant exposure in this population of individuals in whom RV infection may represent a significant health concern.