Asthma is one of the most common childhood diseases. It is chronic and often severely disabling. The amount of nitric oxide that is exhaled while breathing increases with airway inflammation, a symptom of asthma. This study will examine the results from a previous study, the Cincinnati Asthma Prevention (CAP) study, to evaluate the effects of environmental and genetic factors on exhaled nitric oxide (eNO) levels and to determine the relationship between eNO and asthma severity.